Smoke rises during an air strike on an army weapons depot on a mountain overlooking Yemen's capital Sanaa April 20, 2015. REUTERS/Khaled Abdullah TPX IMAGES OF THE DAY

A guard stands on the collapsed roof of the house of General Ali al-Dhafif, a Yemeni army brigade commander, after it was hit by Saudi-led air strikes near Sanaa, Yemen, June 9, 2015. Four people, including two brothers of al-Dhafif, were killed in the strikes, a relative at the scene said. Al-Dhafif was not in or near the house when it was bombarded, the relative added. REUTERS/Khaled Abdullah TPX IMAGES OF THE DAY

A Houthi militant stands amidst debris from a house of a Houthi leader Rafiq Rafiq, which was destroyed by a Saudi-led air strike, near Sanaa May 30, 2015. The Houthi militant is seen holding a picture of Rafiq Rafiq's son, who the Houthis say, was killed in the air-strike which destroyed the house. REUTERS/Mohamed al-Sayaghi 

People flee as smoke billows after air strikes hit the house of Yemen's former President Ali Abdullah Saleh in Sanaa May 10, 2015. Saleh and his family are safe after airstrikes targeted his residence in the capital Sanaa early on Sunday, a news agency allied to the former Yemeni president said. REUTERS/Mohamed al-Sayaghi TPX IMAGES OF THE DAY

A view of a building destroyed by a Saudi-led air strike is seen in Haradh city of Yemen's northwestern province of Hajja May 20, 2015. REUTERS/Stringer 

Fire and smoke billows from an army weapons depot after it was hit by an air strike in Yemen's capital Sanaa May 11, 2015. REUTERS/Mohamed al-Sayaghi TPX IMAGES OF THE DAY

People salvage furniture from the rubble of a house destroyed by an air strike in Sanaa April 26, 2015. Air raids, naval shelling and ground fighting shook Yemen on Sunday in some of the most widespread combat since a Saudi-led alliance intervened last month against Iranian-allied Houthi militia who have seized wide areas of the country. REUTERS/Khaled Abdullah 

People ride on a motorcycle as they pass by a police headquarters destroyed by a Saudi-led air strike in Yemen's northwestern city of Saada May 7, 2015. REUTERS/Khaled Abdullah TPX IMAGES OF THE DAY

Smoke billows from a fire at a Houthi-controlled military site after it was hit by a Saudi-led air strike in Sanaa, Yemen, June 3, 2015. REUTERS/Mohamed al-Sayaghi 

People stand on the rubble of houses destroyed by an air strike in the Okash village near Sanaa April 4, 2015. An air strike on a village near the Yemeni capital Sanaa killed a family of nine, residents said on Saturday, in what appeared to be a hit by the Saudi-led military campaign against Houthi militia. REUTERS/Mohamed al-Sayaghi TPX IMAGES OF THE DAY

A Houthi militant sits amidst debris from the Yemeni Football Association building, which was damaged in a Saudi-led air strike, in Sanaa May 31, 2015. REUTERS/Mohamed al-Sayaghi 

Fire and smoke billows from an army weapons depot after it was hit by an air strike in Yemen's capital Sanaa May 11, 2015. REUTERS/Mohamed al-Sayaghi 

School books are seen on the rubble of houses destroyed by a Saudi-led air strike near Yemen's capital Sanaa June 3, 2015. Air strikes by a Saudi-led Arab alliance shook Yemen's capital Sanaa on Wednesday, mainly targeting military bases aligned with the dominant Houthi group, residents said. REUTERS/Khaled Abdullah 

Houthi militants guard the house of Ali Haidar, a Houthi leader, destroyed by a Saudi-led air strike in Sanaa, Yemen, May 29, 2015. A guard was reportedly injured in the strike on the house, whose occupants had already evacuated prior to the strike, according to Houthis guarding the site and local media. REUTERS/Khaled Abdullah 

A man screams in front of the residence of Yemen's former President Ali Abdullah Saleh after airstrikes hit it in Sanaa May 10, 2015. Saleh and his family are safe after airstrikes targeted his residence in the capital Sanaa early on Sunday, a news agency allied to the former Yemeni president said. REUTERS/Mohamed al-Sayaghi TPX IMAGES OF THE DAY

An air strike hits a military site controlled by the Houthi group in Yemen's capital Sanaa May 12, 2015. REUTERS/Khaled Abdullah 

Houthi militants guard the house of Ali Haidar, a Houthi leader, destroyed by a Saudi-led air strike in Sanaa, Yemen, May 29, 2015. A guard was reportedly injured in the strike on the house, whose occupants had already evacuated prior to the strike, according to Houthis guarding the site and local media. REUTERS/Khaled Abdullah 

People gather at a site hit by a Saudi-led air strike in Yemen's capital Sanaa May 27, 2015. Saudi-led air strikes killed at least 80 people near Yemen's border with Saudi Arabia and in the capital Sanaa on Wednesday, residents said, the deadliest day of bombing in over two months of war in Yemen. REUTERS/Khaled Abdullah 

The collapsed house of General Ali al-Dhafif, a Yemeni army brigade commander, is seen after it was hit by Saudi-led air strikes near Sanaa, Yemen, June 9, 2015. Four people, including two brothers of al-Dhafif, were killed in the strikes, a relative at the scene said. Al-Dhafif was not in or near the house when it was bombarded, the relative added. REUTERS/Khaled Abdullah 

A plainclothes presidential guard stands in front of the residence of Yemen's former President Ali Abdullah Saleh after airstrikes destroyed it in Sanaa May 10, 2015. Saleh and his family are safe after airstrikes targeted his residence in the capital Sanaa early on Sunday, a news agency allied to the former Yemeni president said. REUTERS/Mohamed al-Sayaghi