A hooded youth prepares to throw a petrol bomb during clashes with riot police as Greek students demonstrate against a draft bill changing university entrance requirements in Athens, Greece, October 29, 2018. REUTERS/Alkis Konstantinidis

A masked protester throws a petrol bomb during a demonstration called by self-proclaimed anarchists from the Balkans against nationalism in Thessaloniki, Greece, March 10, 2018. REUTERS/Alexandros Avramidis

A masked protester throws a petrol bomb during a demonstration called by self-proclaimed anarchists from the Balkans against nationalism in Thessaloniki, Greece, March 10, 2018. REUTERS/Alexandros Avramidis

A man inspects damage at a gas station after air strikes in the city of Saada, Yemen January 6, 2018. REUTERS/Naif Rahma

A riot police officer is engulfed in flames by a petrol bomb during riots outside the parliament building as Greek lawmakers vote on the latest round of austerity Greece has agreed with its lenders, in Athens REUTERS/Costas Baltas TPX IMAGES OF THE DAY

Riot police walk among flames by petrol bombs as a guard post of the Tomb of the Unknown Soldier burns during clashes outside the parliament building as Greek lawmakers vote on the latest round of austerity Greece has agreed with its lenders, in Athens, Greece, May 18, 2017. REUTERS/Costas Baltas TPX IMAGES OF THE DAY

A woman reacts next to a reporter injured by an improvised bomb during a protest against the rising prices of gasoline enforced by the Mexican government at the Macroplaza in Monterrey, Mexico, January 5, 2017. REUTERS/Daniel Becerril

Chemical experts inspect the site of a suicide truck bomb attack, at a petrol station in the city of Hilla, south of Baghdad, Iraq, November 25, 2016. REUTERS/Alaa Al-Marjani TPX IMAGES OF THE DAY

Iraqi security forces gather at the site of a suicide truck bomb attack, at a petrol station in the city of Hilla south of Baghdad, Iraq, November 24, 2016. REUTERS/Alaa Al-Marjani

People gather at the site of a suicide truck bomb attack, at a petrol station in the city of Hilla south of Baghdad, Iraq, November 24, 2016. REUTERS/Alaa Al-Marjani

Iraqi security forces inspect the site of a suicide truck bomb attack, at a petrol station in the city of Hilla south of Baghdad, Iraq, November 24, 2016. REUTERS/Alaa Al-Marjani

Iraqi security forces inspect the site of a suicide truck bomb attack, at a petrol station in the city of Hilla south of Baghdad, Iraq, November 24, 2016. REUTERS/Alaa Al-Marjani

People gather at the site of a suicide truck bomb attack, at a petrol station in the city of Hilla south of Baghdad, Iraq, November 24, 2016. REUTERS/Alaa Al-Marjani

A man reacts at the site of a suicide truck bomb attack, at a petrol station in the city of Hilla south of Baghdad, Iraq, November 24, 2016. REUTERS/Alaa Al-Marjani

Iraqi security forces gather at the site of a suicide truck bomb attack, at a petrol station in the city of Hilla south of Baghdad, Iraq, November 24, 2016. REUTERS/Alaa Al-Marjani

A man reacts at the site of a suicide truck bomb attack, at a petrol station in the city of Hilla south of Baghdad, Iraq, November 24, 2016. REUTERS/Alaa Al-Marjani

A man reacts at the site of a suicide truck bomb attack, at a petrol station in the city of Hilla south of Baghdad, Iraq, November 24, 2016. REUTERS/Alaa Al-Marjani TPX IMAGES OF THE DAY

Iraqi men react at the site of a suicide truck bomb attack, at a petrol station in the city of Hilla south of Baghdad, Iraq, November 24, 2016. REUTERS/Alaa Al-Marjani

Iraqi security forces gather at the site of a suicide truck bomb attack, at a petrol station in the city of Hilla south of Baghdad, Iraq, November 24, 2016. REUTERS/Alaa Al-Marjani

A man reacts at the site of a suicide truck bomb attack, at a petrol station in the city of Hilla south of Baghdad, Iraq, November 24, 2016. REUTERS/Alaa Al-Marjani TPX IMAGES OF THE DAY

Policemen run between exploding petrol bombs during clashes following a rally marking the 43nd anniversary of a 1973 student uprising against the military dictatorship that was ruling Greece, in Athens, Greece, November 17, 2016. REUTERS/Alkis Konstantinidis TPX IMAGES OF THE DAY

Riot policemen try to extinguish flames from a petrol bomb on a colleague during clashes following a rally marking the 43nd anniversary of a 1973 student uprising against the military dictatorship that was ruling Greece, in Athens, Greece, November 17, 2016. REUTERS/Alkis Konstantinidis

A petrol bomb explodes among riot policemen during clashes following a rally marking the 43nd anniversary of a 1973 student uprising against the military dictatorship that was ruling Greece, in Athens, Greece, November 17, 2016. REUTERS/Alkis Konstantinidis

A petrol bomb explodes among riot policemen during clashes following a rally marking the 43nd anniversary of a 1973 student uprising against the military dictatorship that was ruling Greece, in Athens, Greece, November 17, 2016. REUTERS/Alkis Konstantinidis

A petrol bomb explodes next to riot police during a demonstration against the visit of U.S President Barack Obama, in Athens, Greece, November 15, 2016. REUTERS/Michalis Karagiannis

A petrol bomb explodes next to riot police during a demonstration against the visit of U.S President Barack Obama, in Athens, Greece, November 15, 2016. REUTERS/Michalis Karagiannis

A petrol bomb explodes next to riot police during a demonstration against the visit of U.S President Barack Obama, in Athens, Greece, November 15, 2016. REUTERS/Michalis Karagiannis

A petrol bomb explodes next to riot police during a demonstration against the visit of U.S President Barack Obama, in Athens, Greece, November 15, 2016. REUTERS/Alkis Konstantinidis

A petrol bomb explodes next to riot police during a demonstration against the visit of U.S President Barack Obama, in Athens, Greece, November 15, 2016. REUTERS/Alkis Konstantinidis

A hooded youth throws a petrol bomb at riot police standing guard at the parliament premises, during a demonstration of school students against education reforms, in Athens, Greece, November 7, 2016. REUTERS/Alkis Konstantinidis

A demonstrator prepares to throw a molotov cocktail towards riot police officers during a protest called by university students against Venezuela's government in Caracas, Venezuela, June 9, 2016. REUTERS/Carlos Garcia Rawlins

A demonstrator throws a molotov cocktail against riot policemen during a protest called by university students against Venezuela's government in Caracas, Venezuela, June 9, 2016. REUTERS/Carlos Garcia Rawlins TPX IMAGES OF THE DAY

A masked youth prepares to throw a petrol bomb at riot police during clashes marking a 24-hour general strike against planned pension reforms in Athens, Greece, February 4, 2016. REUTERS/Alkis Konstantinidis

Riot police react to petrol bombs thrown by masked youths in Syntagma Square during a 24-hour general strike against planned pension reforms in Athens, Greece, February 4, 2016. REUTERS/Alkis Konstantinidis TPX IMAGES OF THE DAY

Riot police react to petrol bombs thrown by masked youths in Syntagma Square during a 24-hour general strike against planned pension reforms in Athens, Greece, February 4, 2016. REUTERS/Alkis Konstantinidis TPX IMAGES OF THE DAY

Petrol bombs thrown by demonstrators explode near riot police officers in Syntagma Square, during a 24-hour general strike against planned pension reforms in Athens, Greece, February 4, 2016. REUTERS/Alkis Konstantinidis

A masked demonstrator throws a petrol bombs to riot police in Syntagma Square, during a 24-hour general strike against planned pension reforms in Athens, Greece, February 4, 2016. REUTERS/Alkis Konstantinidis

Riot police react to petrol bombs thrown by masked youths in Syntagma Square during a 24-hour general strike against planned pension reforms in Athens, Greece, February 4, 2016. REUTERS/Alkis Konstantinidis

Riot police react to petrol bombs thrown by masked youths in Syntagma Square during a 24-hour general strike against planned pension reforms in Athens, Greece, February 4, 2016. REUTERS/Alkis Konstantinidis

Riot police react to petrol bombs thrown by masked youths in Syntagma Square during a 24-hour general strike against planned pension reforms in Athens, Greece, February 4, 2016. REUTERS/Alkis Konstantinidis

Riot police react to petrol bombs thrown by masked youths in Syntagma Square during a 24-hour general strike against planned pension reforms in Athens, Greece, February 4, 2016. REUTERS/Alkis Konstantinidis

Riot police stand guard during clashes with hooded youth seen in the background, following an anniversary rally marking the 2008 police shooting of 15-year-old student, Alexandros Grigoropoulos, in Athens, Greece, December 6, 2015. REUTERS/Alkis Konstantinidis TPX IMAGES OF THE DAY

A riot police officer walks amidst fires caused by petrol bombs thrown away by hooded youth during clashes, following an anniversary rally marking the 2008 police shooting of 15-year-old student, Alexandros Grigoropoulos, in Athens, Greece, December 6, 2015. REUTERS/Alkis Konstantinidis

A petrol bomb explodes next to a riot police officer during clashes with hooded youth following an anniversary rally marking the 2008 police shooting of 15-year-old student, Alexandros Grigoropoulos, in Athens, Greece, December 6, 2015. REUTERS/Alkis Konstantinidis

A petrol bomb explodes next to a riot police officer during clashes with hooded youth following an anniversary rally marking the 2008 police shooting of 15-year-old student, Alexandros Grigoropoulos, in Athens, Greece, December 6, 2015. REUTERS/Alkis Konstantinidis TPX IMAGES OF THE DAY

A Palestinian protester uses a sling to throw stones at Israeli troops as another prepares a molotov cocktail during clashes near the Jewish settlement of Bet El, near the West Bank city of Ramallah November 16, 2015. REUTERS/Mohamad Torokman

A riot policeman runs through a fire caused by petrol bomb thrown by youths during brief clashes between police and protesters during a 24-hour general strike in central Athens, Greece, November 12, 2015. Domestic flights will be grounded, ships will remain docked at ports and public offices will shut on Thursday as Greeks walk off the job to protest austerity measures demanded by international lenders in exchange for fresh bailout funds. REUTERS/Yannis Behrakis

Fire caused by petrol bombs thrown by youths is seen at the building of Greece's central bank following brief clashes between police and protesters during a 24-hour general strike in central Athens, Greece November 12, 2015. Striking Greeks took to the streets on Thursday to protest austerity measures, setting Alexis Tsipras' government its biggest domestic challenge since he was re-elected in September on a promise to cushion the impact of economic hardship. The fire was extinguished without causing serious damage. REUTERS/Alkis Konstantinidis TPX IMAGES OF THE DAY

Nepalese police personnel take cover as protesters (unseen) throw petrol bombs towards them during a general strike called by the Madhesi protesters demonstrating against the new constitution in Birgunj, Nepal November 4, 2015. Nepal has faced an acute fuel crisis for more than a month since protesters in the lowland south, angered that a new constitution fails to reflect their interests, prevented supply trucks from entering from India. Many in Nepal see India's hand in the protests although it denies any role. REUTERS/Navesh Chitrakar

A protester (C) throws a petrol bomb towards Nepalese police personnel (unseen) during a general strike called by the Madhesi protesters protesting against the new constitution in Birgunj, Nepal November 4, 2015. Nepal has faced an acute fuel crisis for more than a month since protesters in the lowland south, angered that a new constitution fails to reflect their interests, prevented supply trucks from entering from India. Many in Nepal see India's hand in the protests although it denies any role. REUTERS/Navesh Chitrakar

Palestinian protesters put out a fire burning on a compatriot, caused by a molotov cocktail which he was trying to hurl at Israeli troops during clashes in the West Bank city of Hebron October 13, 2015. Seven Israelis and 27 Palestinians, including nine alleged attackers and eight children, have died in almost two weeks of street attacks and security crackdowns. The violence has been stirred in part by Muslim anger over increasing Jewish visits to the al-Aqsa mosque compound in Jerusalem, Islam's holiest site outside the Arabian Peninsula. REUTERS/Mussa Qawasma

Palestinian protesters put out a fire burning on a compatriot, caused by a molotov cocktail which he was trying to hurl at Israeli troops during clashes in the West Bank city of Hebron October 13, 2015. Seven Israelis and 27 Palestinians, including nine alleged attackers and eight children, have died in almost two weeks of street attacks and security crackdowns. The violence has been stirred in part by Muslim anger over increasing Jewish visits to the al-Aqsa mosque compound in Jerusalem, Islam's holiest site outside the Arabian Peninsula. REUTERS/Mussa Qawasma

A Palestinian protester throws a molotov cocktail at Israeli troops during clashes in the West Bank city of Hebron October 13, 2015. Seven Israelis and 27 Palestinians, including nine alleged attackers and eight children, have died in almost two weeks of street attacks and security crackdowns.The violence has been stirred in part by Muslim anger over increasing Jewish visits to the al-Aqsa mosque compound in Jerusalem, Islam's holiest site outside the Arabian Peninsula. REUTERS/Mussa Qawasma

Palestinian protesters put out a fire burning on a compatriot, caused by a molotov cocktail which he was trying to hurl at Israeli troops during clashes in the West Bank city of Hebron October 13, 2015. Seven Israelis and 27 Palestinians, including nine alleged attackers and eight children, have died in almost two weeks of street attacks and security crackdowns. The violence has been stirred in part by Muslim anger over increasing Jewish visits to the al-Aqsa mosque compound in Jerusalem, Islam's holiest site outside the Arabian Peninsula. REUTERS/Mussa Qawasma TPX IMAGES OF THE DAY

Protesters throw molotov cocktail at the police during clashes in Pristina, the capital of Kosovo October 12, 2015. Protesters besieged the central police station in Kosovo on Monday, hours after the arrest of a prominent opposition politician, lobbing concrete and stones at police who returned fire with teargas. REUTERS/Hazir Reka

Police are seen next to fire caused by molotov cocktail thrown by protesters, at Kosovo's capital Pristina October 12, 2015. Protesters besieged the central police station in Kosovo on Monday, hours after the arrest of a prominent opposition politician, lobbing concrete and stones at police who returned fire with teargas. REUTERS/Hazir Reka TPX IMAGES OF THE DAY

A Molotov cocktail is thrown by Palestinians at an Israeli army jeep during clashes near the Jewish settlement of Bet El, near the West Bank city of Ramallah October 8, 2015. Four people, including an Israeli soldier, were stabbed and wounded near a military headquarters in Tel Aviv on Thursday, police and ambulance sources said, as a rash of such Palestinian attacks spread to Israel's commercial capital. REUTERS/Mohamad Torokman TPX IMAGES OF THE DAY

Palestinian protesters throw a molotov cocktail towards Israeli troops during clashes near the Jewish settlement of Bet El, near the occupied West Bank city of Ramallah October 5, 2015. Violence intensified in Jerusalem and the West Bank on Sunday after Israelis were targeted in two stabbing attacks and a Palestinian was killed in a clash with Israeli troops, officials said. REUTERS/Mohamad Torokman

A hooded demonstrator prepares to throw a Molotov cocktail against riot policemen during a protest marking the country's 1973 military coup, in Santiago, Chile September 13, 2015. Chile marks the start of the coup d'etat that ushered in a 17-year dictatorship under General Augusto Pinochet on September 11. REUTERS/Ivan Alvarado

A hooded demonstrator throws a Molotov cocktail at a riot police vehicle (not pictured) as a rainbow is seen on the ground during a protest marking the country's 1973 military coup, in Santiago, Chile September 13, 2015. Chile marks the start of the coup d'etat that ushered in a 17-year dictatorship under General Augusto Pinochet on September 11. REUTERS/Ivan Alvarado