Iraqi special forces soldiers fire a mortar round at Islamic State fighters positions in Tahrir neighbourhood of Mosul, Iraq, November 17, 2016. REUTERS/Goran Tomasevic

An Iraqi soldier prepares to fire a mortar in a village outside Mosul, Iraq November 9, 2016. REUTERS/Goran Tomasevic 

Smoke rises after a mortar is fired by Islamic State militants at Kurdish Peshmerga forces during a battle at Topzawa village, near Bashiqa near Mosul, Iraq October 24, 2016. REUTERS/Ahmed Jadallah 

Homemade mortars belonging to Islamic State militants are seen in the town of Gwer northern Iraq August 31, 2016. Picture taken August 31, 2016. REUTERS/Azad Lashkari 

Ethnic Armenian soldiers stand next to a cannon at artillery positions near the Nagorno-Karabakh's town of Martuni, April 7, 2016. REUTERS/Staff TPX IMAGES OF THE DAY

Shi'ite fighters launch a mortar round towards Islamic State militants in al-Fatha, northeast of Baiji, October 18, 2015. Iraqi forces backed by Shi'ite militia fighters say they have retaken a mountain palace complex of former President Saddam Hussein from Islamic State fighters, as government forces push ahead on a major offensive against the insurgents. REUTERS/Thaier Al-Sudani

A fighter of the anti-Houthi Popular Resistance Committees prepares a mortar cannon during fighting with Houthi fighters near Yemen's northern city of Marib May 29, 2015. REUTERS/Stringer 

Rebel fighters fire a locally made shell during clashes with forces loyal to Syria's President Bashar al-Assad on the frontline of Aleppo's Sheikh Saeed neighbourhood May 23, 2015. Rebel fighters from Al-Fawj al-Awal, al-Safwa battalions and group 101 brigades, that are part of the Free Syrian Army, made advances against forces loyal to Syria's President Bashar al-Assad during Aleppo Intifada battles, they said. Picture taken May 23, 2015. REUTERS/Hosam Katan

A Saudi soldier fires a mortar towards Houthi movement position, at the Saudi border with Yemen April 21, 2015. REUTERS/Stringer TPX IMAGES OF THE DAY

A fighter from Liwa al-Nasr (Victory Brigade) fires a mortar shell towards forces loyal to Syria's President Bashar Al-Assad in Turkmen mountains, Latakia countryside April 18, 2015. Picture taken April 18. REUTERS/Khalil Ashawi TPX IMAGES OF THE DAY

A rebel fighter of al-Jabha al-Shamiya (the Shamiya Front) is seen through the scope of a new locally made cannon named "al-Qannas" (Sniper) before launching it towards forces loyal to Syria's President Bashar al-Assad stationed in Hanano barracks in Aleppo April 8, 2015. The cannon is decorated with two mock rockets. REUTERS/Abdalrhman Ismail 

Ansar Al-Sham Brigade fighters fire their weapons towards warplanes loyal to Syria's President Bashar Al-Assad, activists said, near Jisr al-Shoghour, Idlib province March 25, 2015. Picture taken March 25, 2015. REUTERS/Mohamad Bayoush 

A rebel fighter from the Ahrar al-Sham Islamic Movement sits inside a trench loaded with mortar shells near one of the fronts in Morek city in the northern countryside of Hama March 16, 2015. REUTERS/Khalil Ashawi (SYRIA - Tags: POLITICS CIVIL UNREST CONFLICT MILITARY) 

Rebel fighters prepare to fire a mortar towards forces loyal to Syria's President Bashar al-Assad who are stationed in Tel Merhi and Deir Adass villages, from the northwestern countryside of Deraa February 18, 2015. Heavy fighting in southern Syria has killed scores of pro-government and insurgent fighters in the past week, a group monitoring Syria's war said on Sunday, forecasting even fiercer violence as the weather clears. Picture taken February 18. REUTERS/Wsam Almokdad (SYRIA - Tags: POLITICS CIVIL UNREST CONFLICT MILITARY TPX IMAGES OF THE DAY) 

Members of al Qaeda's Nusra Front prepare to fire a mortar towards forces loyal to Syria's President Bashar al-Assad in al-Mallah farms, north of Aleppo, February 18, 2015. Battles in and around the Syrian city of Aleppo have killed at least 70 pro-government fighters and more than 80 insurgents after the army launched an offensive there, a monitoring group said on Wednesday.The army backed by allied militia had captured areas north of Aleppo on Tuesday in what the Syrian Observatory for Human Rights said was an attempt to encircle the northern city and cut off insurgent supply lines. REUTERS/Hosam Katan (SYRIA - Tags: CIVIL UNREST POLITICS CONFLICT) 

A mortar flies out of a tube during a mortar exercise for U.S. soldiers in Dragon Company of the 3rd Cavalry Regiment near forward operating base Gamberi in the Laghman province of Afghanistan December 26, 2014. REUTERS/Lucas Jackson (AFGHANISTAN - Tags: CONFLICT POLITICS MILITARY TPX IMAGES OF THE DAY) 

Locally made shells are launched by Free Syrian Army fighters towards forces loyal to Syria's President Bashar al-Assad in the Handarat area, north of Aleppo November 30, 2014. REUTERS/Hosam Katan (SYRIA - Tags: POLITICS CIVIL UNREST CONFLICT MILITARY) 

A member of the Kurdish Peshmerga force fires a mortar at Sulaiman Pek front line in the northwest of Tikrit city August 31, 2014. REUTERS/Youssef Boudlal (IRAQ - Tags: CIVIL UNREST POLITICS MILITARY TPX IMAGES OF THE DAY) 

A Hamas militant displays a mortar shell as he celebrates what the militants say was a victory over Israel, in front of a destroyed house in the Shejaia neighborhood east of Gaza City August 27, 2014. An open-ended ceasefire in the Gaza war held on Wednesday as Prime Minister Benjamin Netanyahu faced strong criticism in Israel over a costly conflict with Palestinian militants in which no clear victor emerged. REUTERS/Majdi Fathi (GAZA - Tags: POLITICS CONFLICT TPX IMAGES OF THE DAY) 

A Colombian soldier demonstrates the assembly process of a handmade mortar shell, during a news conference in Cali August 15, 2014. Colombia's army has raided and shut down a factory producing handmade explosive devices in the rural area of municipality of Suarez, Cauca. Authorities said that the factory, which belonged to the Revolutionary Armed Forces of Colombia (FARC), was capable of producing about 200 mortars every week. REUTERS/Jaime Saldarriaga (COLOMBIA - Tags: MILITARY CRIME LAW CIVIL UNREST) 

Israeli soldiers fire a mortar towards the Gaza Strip July 22, 2014. Israel pounded targets across the Gaza Strip on Tuesday, saying no ceasefire was near as top U.S. and U.N. diplomats pursued talks on halting fighting that has claimed more than 500 lives. With the conflict entering its third week, the Palestinian death toll rose to 546, including nearly 100 children and many other civilians, Gaza health officials said. Israel's casualties also mounted, with the military announcing the deaths of two more soldiers, bringing the number of army fatalities to 27 - almost three times as many as were killed in the last ground invasion of Gaza, in a 2008-2009 war. REUTERS/Amir Cohen (ISRAEL - Tags: CONFLICT POLITICS CIVIL UNREST TPX IMAGES OF THE DAY) 

German armed forces Bundeswehr soldiers fire mortars during the JAWTEX 2014 (Joint Air Warfare Tactical Exercise) at an army training area in Bergen, May 20, 2014. About 4500 soldiers from eleven countries take part at the largest European military exercise in 2014. REUTERS/Fabrizio Bensch (GERMANY - Tags: MILITARY) 

An anti-government protester fires a homemade mortar towards police during a demonstration in which masked youths battled police and blocked a main highway in Caracas April 21, 2014. Anti-Maduro protests since early February have led to violence killing at least 41 people, according to official figures. The dead have been from both sides of the South American nation's political divide and from security forces. REUTERS/Christian Veron (VENEZUELA - Tags: CIVIL UNREST POLITICS TPX IMAGES OF THE DAY) 

An anti-government protester fires a rudimentary mortar at the police during a protest against President Nicolas Maduro's government in Caracas April 12, 2014. Maduro cautioned opposition leaders to keep their expectations modest on Thursday as he hosted them for mediated talks intended to stem two months of deadly political unrest. REUTERS/Carlos Garcia Rawlins (VENEZUELA - Tags: POLITICS CIVIL UNREST TPX IMAGES OF THE DAY) 

Anti-government protesters fire a rudimentary mortar at the police during riots in Caracas April 6, 2014. Protesters have been on the streets since early February calling for President Nicolas Maduro's resignation and complaining about a litany of problems from rampant crime to food shortages.The government says they are seeking a coup against Maduro. REUTERS/Carlos Garcia Rawlins (VENEZUELA - Tags: POLITICS CIVIL UNREST) 

Rebel fighters carry mortar shells during clashes in the town of Babolin in Idlib countryside with forces loyal to Syria's President Bashar al-Assad April 4, 2014. Islamist rebels in Syria have retaken a northern town on the main north-south highway from President Bashar al-Assad's forces, the Syrian Observatory for Human Rights said on Friday. The monitoring group said rebels killed 18 soldiers and disabled two tanks in the fight for the town of Babolin, part of an offensive along a stretch of the highway which links Damascus to the northern city of Aleppo. Picture taken April 4, 2014. REUTERS/Stringer (SYRIA - Tags: POLITICS CIVIL UNREST CONFLICT TPX IMAGES OF THE DAY) 

A mortar shell is fired towards forces loyal to the Syrian regime in town of Morek in Hama province, a town on the highway that runs from Hama to Aleppo March 6, 2014. Picture taken March 6, 2014. REUTERS/Ahmad Rif (SYRIA - Tags: POLITICS CIVIL UNREST CONFLICT) 

A Free Syrian Army fighter runs to take cover after launching a mortar towards forces loyal to Syria's President Bashar al-Assad in the Jabal al-Akrad area in Syria's northwestern Latakia province February 25, 2014. Picture taken February 25, 2014. REUTERS/Alaa Khweled (SYRIA - Tags: POLITICS CIVIL UNREST CONFLICT TPX IMAGES OF THE DAY) 

Free Syrian Army fighters prepare to launch a mortar shell towards forces loyal to Syria's President Bashar al-Assad in Khan Shaikhoun in Idlib, February 14, 2014. Picture taken February 14, 2014. REUTERS/Abdalghne Karoof (SYRIA - Tags: POLITICS CIVIL UNREST CONFLICT) 

Free Syrian Army fighters fire a homemade mortar at Karm al-Tarab neighborhood in Aleppo January 27, 2014. Picture taken January 27, 2014. REUTERS/Ammar Abdullah (SYRIA - Tags: POLITICS CIVIL UNREST CONFLICT) 

A Free Syrian Army fighter holds a mortar shell in Arkoub area of Aleppo, December 21, 2013. Picture taken December 21, 2013. REUTERS/Mohamed Mounzer Masri (SYRIA - Tags: POLITICS CIVIL UNREST CONFLICT) 

Free Syrian Army fighters clean a homemade mortar in Deir al-Zor, eastern Syria December 2, 2013. REUTERS/Khalil Ashawi (SYRIA - Tags: POLITICS CIVIL UNREST CONFLICT) 

Free Syrian Army fighters fire a homemade mortar from Maaret al-Naaman town towards the Wadi al-Deif military base, where forces loyal to Syria's President Bashar al-Assad are located, in Idlib November 18, 2013. Picture taken November 18, 2013. REUTERS/Houssam Abo Dabak (SYRIA - Tags: CIVIL UNREST MILITARY POLITICS CONFLICT) 

A Free Syrian Army fighter launches a rocket towards forces loyal to President Bashar Al-Assad in Raqqa October 18, 2013. REUTERS/Nour Fourat (SYRIA - Tags: POLITICS CIVIL UNREST CONFLICT TPX IMAGES OF THE DAY) 

A mortar shell is launched by Free Syrian Army fighters towards forces loyal to Syria's President Bashar al-Assad in Ain-Assan village in Aleppo, October 4, 2013. REUTERS/Molhem Barakat (SYRIA - Tags: CIVIL UNREST CONFLICT) 

A member of the 'Ansar Dimachk' Brigade, part of the 'Asood Allah' Brigade which operates under the Free Syrian Army, uses an iPad during preparations to fire a homemade mortar at one of the battlefronts in Jobar, Damascus September 15, 2013. REUTERS/ Mohamed Abdullah (SYRIA - Tags: POLITICS CIVIL UNREST CONFLICT TPX IMAGES OF THE DAY) FOR BEST QUALITY IMAGE: ALSO SEE GM1E99O1RH801. 

Philippine Red Cross personnel react after a mortar attack by Muslim rebels, near the scene of fighting between government soldiers and Muslim rebels from the Moro National Liberation Front (MNLF) in Zamboanga city in southern Philippines September 13, 2013. REUTERS/Erik De Castro (PHILIPPINES - Tags: CIVIL UNREST CONFLICT POLITICS) 

Issa, 10 years old, carries a mortar shell in a weapons factory of the Free Syrian Army in Aleppo, September 7, 2013. Issa works with his father in the factory for ten hours every day except on Fridays. REUTERS/Hamid Khatib (SYRIA - Tags: POLITICS CONFLICT CIVIL UNREST TPX IMAGES OF THE DAY) FOR BEST QUALITY IMAGE ALSO SEE: GM1E9A41HAT01 

A Free Syrian Army fighter spray paints on improvised mortar shells at a weapon factory in Aleppo September 5, 2013. REUTERS/Hamid Khatib (SYRIA - Tags: POLITICS CIVIL UNREST CONFLICT) 

A Free Syrian Army fighter spray paints an improvised mortar shell, as his fellow fighter watches him, in Aleppo September 4, 2013. REUTERS/Hamid Khatib (SYRIA - Tags: POLITICS CIVIL UNREST CONFLICT TPX IMAGES OF THE DAY) 

A member of the "Free Men of Syria" (Ahrar Suriya) brigade, operating under the Free Syrian Army, works on an improvised mortar shell at a factory in Aleppo countryside, August 26, 2013. REUTERS/Muzaffar Salman (SYRIA - Tags: POLITICS CONFLICT) 

A Free Syrian Army fighter prepares mortar shells in Aleppo August 1, 2013. REUTERS/Hamid Khatib (SYRIA - Tags: CONFLICT) 

Free Syrian Army fighters prepare a mortar in Aleppo's Salaheddine neighbourhood July 9, 2013. Picture taken July 9, 2013. REUTERS/Ammar Abdullah (SYRIA - Tags: CONFLICT) 

A Free Syrian Army fighter uses a laptop as another prepares to fire a mortar launcher at the frontline near Nairab military airport, which is controlled by forces loyal to Syria's President Bashar al-Assad, in Aleppo, June 14, 2013. REUTERS/Hamid Khatib (SYRIA - Tags: CONFLICT) 

A Free Syrian Army fighter carries a mortar launcher at the frontline near Nairab airport, which is controlled by forces loyal to Syria's President Bashar al-Assad, in Aleppo, June 14, 2013. REUTERS/Hamid Khatib (SYRIA - Tags: CONFLICT) 

A member of the Free Syrian Army works on an improvised mortar shell in Deir al-Zor March 8, 2013. Picture taken March 8, 2013. REUTERS/ Khalil Ashawi (SYRIA - Tags: CIVIL UNREST MILITARY POLITICS CONFLICT) 

Members of the Free Syrian Army work on an improvised mortar shell in Deir al-Zor March 8, 2013. Picture taken March 8, 2013. REUTERS/ Khalil Ashawi (SYRIA - Tags: CONFLICT MILITARY POLITICS CIVIL UNREST) 

A Free Syrian Army fighter walks through a dust-filled stairwell after a comrade fired a B-10 recoilless gun at Syrian Army soldiers in the Haresta neighbourhood of Damascus in this February 7, 2013 file photo. The antiquated, probably 1960s vintage, Soviet B-10 recoilless rifle, is a heavy, bazooka-style cannon normally mounted on a little trolley and weighing about 70 kg (150 pounds); the rebel fighter simply hefted it onto his shoulder and blasted a heavy round somewhere down the road. In a month on the frontline Goran Tomasevic documented rebel fighters as they defended a swathe of suburbs, mounted complex mass attacks, managed logistics, treated their wounded - and died. But as constant, mortar, tank and sniper fire attested, President Bashar al-Assad's soldiers, often just a room or a grenade toss away, were equally well drilled - and much better armed. Picture taken February 7, 2013. REUTERS/Goran Tomasevic/Files (SYRIA - Tags: CIVIL UNREST POLITICS CONFLICT)

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A 60mm mortar round is handed in by a resident during the '"Voluntary Disarmament Programme" at the atrium of the Saint Kings parish in Mexico City February 19, 2013. The programme, run by the Mexico City government with support of the Army and the Catholic Church, aims to swap weapons for money or a tablet to promote voluntary disarmament and avoid accidents, local media reported. REUTERS/Tomas Bravo (MEXICO - Tags: CRIME LAW SOCIETY) 

Free Syrian Army fighters set up mortar bombs, pointing towards Nairab military airport and the international airport, which are controlled by forces loyal to Syria's President Bashar al-Assad in Aleppo, February 19, 2013. REUTERS/Muzaffar Salman (SYRIA - Tags: POLITICS CIVIL UNREST CONFLICT TPX IMAGES OF THE DAY) 

A Free Syrian Army fighter holds an improvised mortar shell inside a factory which previously manufactured steel and iron in Aleppo February 18, 2013. REUTERS/Hamid Khatib (SYRIA - Tags: CIVIL UNREST MILITARY POLITICS CONFLICT) 

A man sits near parts of an improvised mortar shell produced for the Free Syrian Army inside a factory which previously manufactured steel and iron in Aleppo February 18, 2013. REUTERS/Hamid Khatib (SYRIA - Tags: CONFLICT POLITICS CIVIL UNREST) 

U.S. soldiers of B Troop, 1st squadron of 4th US Cavalry Regiment, fire a 120 mm mortar shell during a mortar registration exercise at COP (Combat outpost) Sar Howza in Paktika province October 29, 2012. REUTERS/Goran Tomasevic (AFGHANISTAN - Tags: CIVIL UNREST MILITARY TPX IMAGES OF THE DAY) 

A M23 rebel fighter holds an 82mm mortar bomb at a defense position in Karambi, eastern Democratic Republic of Congo (DRC) in north Kivu province, near the border with Uganda, July 12, 2012. Democratic Republic of Congo, Rwanda and neighbouring states called on Thursday for the creation of an international military force to eliminate armed rebels in turbulent eastern Congo. Congo's government, whose army has retreated in disarray before the advancing M23 rebels over the last week, had accused neighbour Rwanda of fomenting and supporting the rebellion, which began as a mutiny by former rebels in the government army. REUTERS/James Akena (DEMOCRATIC REPUBLIC OF CONGO - Tags: SOCIETY CIVIL UNREST MILITARY POLITICS) 

A student from the Universidad Agraria (UNA) public university prepares to fire a homemade mortar on the Panamerican highway in Managua June 5, 2012. Dozens of students blocked the highway to demand internal elections at the public university after what they say was electoral fraud during the recent May 29 university elections. REUTERS/Oswaldo Rivas (NICARAGUA - Tags: CIVIL UNREST EDUCATION) 

A soldier from the Kazakhstan Army's Air Mobile Force fires a mortar during a drill at Koktal range, some 300 km (186 miles) east of Almaty February 15, 2012. Picture taken February 15, 2012. REUTERS/Shamil Zhumatov (KAZAKHSTAN - Tags: MILITARY) 

An unexploded mortar shell, left from recent fighting between security forces and tribal militants loyal to the powerful al-Ahmar family, is seen on a road in the vicinity of government buildings in the Yemeni capital Sanaa January 17, 2012. REUTERS/Khaled Abdullah (YEMEN - Tags: POLITICS CIVIL UNREST MILITARY) 

A U.S. soldier from Alpha Co, 2nd Battalion 35th Infantry, Task Force "Cacti", throws away the empty shell of a 120mm mortar after firing successive rounds at Taliban positions in Shalay Valley from Combat Outpost Penich, in Kunar province, near the Afghanistan-Pakistan border October 4, 2011. REUTERS/Erik De Castro (AFGHANISTAN - Tags: MILITARY CIVIL UNREST CONFLICT TPX IMAGES OF THE DAY) 

An anti-Gaddafi fighter fires a mortar during a battle in a village near Sirte, one of Muammar Gaddafi's last remaining strongholds September 17, 2011. REUTERS/Goran Tomasevic (LIBYA - Tags: CIVIL UNREST) 

U.S. soldiers from Alpha Co, 2nd Battalion 35th Infantry, Task Force "Cacti" are enveloped with smoke as they fire 120 mm mortar at the Taliban position from Combat Outpost Penich, in Khas Konar district in Kunar province, eastern Afghanistan September 30, 2011. The soldiers hugged each other while stepping on the base of the mortar to avoid sudden movement. REUTERS/Erik De Castro (AFGHANISTAN - Tags: MILITARY CIVIL UNREST CONFLICT TPX IMAGES OF THE DAY)