Yemeni tribesmen sit on the back of a pick-up truck near a military base in the Yemeni frontline province of Marib September 14, 2015. Gulf Arab coalition forces fighting Houthi militia in Yemen are advancing on the capital in a two-pronged offensive, generals told reporters on Monday at a desert oil compound they have turned into a military base. (Photo by Noah Browning/Reuters)





Debris and smoke rise after a Saudi-led airstrike hits an army base in Sanaa, Yemen, Monday, September 14, 2015. Saudi Arabia is leading a coalition of mainly Gulf nations fighting Shiite Yemeni rebels known as the Houthis, who are allied with army units loyal to former President Ali Abdullah Saleh. (Photo by Hani Mohammed/AP Photo)





A group of soldiers trained by Emirati and Gulf Arab forces along with Yemeni tribesmen gather near a military base in the Yemeni frontline province of Marib September 14, 2015. (Photo by Noah Browning/Reuters)





A group of soldiers trained by Emirati and Gulf Arab forces flash the victory sign near a military base in the Yemeni frontline province of Marib September 14, 2015. (Photo by Noah Browning/Reuters)





A soldier from the United Arab Emirates jumps from an armoured vehicle in the frontline conflict zone of Marib in central Yemen September 14, 2015. (Photo by Noah Browning/Reuters)





A soldier from the United Arab Emirates peers out of his armoured vehicle in the frontline conflict zone of Marib in central Yemen September 14, 2015. (Photo by Noah Browning/Reuters)





An Airman from the Emirati armed forces gives a thumbs up to a colleague during a flight from a base in Saudi Arabia to the frontline Yemeni province of Mareb September 14, 2015. (Photo by Noah Browning/Reuters)





A soldier from the United Arab Emirates armed with a machine gun watches over Yemeni territory on a chinook helicopter flying a small group of journalists to the the frontline conflict zone of Marib in central Yemen September 14, 2015. (Photo by Noah Browning/Reuters)





A soldier and an airman from the United Arab Emirates armed sit in a chinook helicopter flying a small group of journalists to the the frontline conflict zone of Marib in central Yemen September 14, 2015. (Photo by Noah Browning/Reuters)





A soldier looks at smoke billowing from the site of a Saudi-led air strike on a Houthi position in the Yemeni frontline province of Marib September 15, 2015. (Photo by Reuters/Stringer)





Emirati armoured vehicles are seen on the Yemeni front line province of Marib September 15, 2015. (Photo by Reuters/Stringer)





Soldiers loyal to the Yemeni government take positions during fighting with Houthi militiamen in the Yemeni frontline province of Marib September 16, 2015. (Photo by Reuters/Stringer)





A soldier walks at the site of a Saudi-led air strike in Yemen's capital Sanaa September 16, 2015. (Photo by Khaled Abdullah/Reuters)





People gather at the site of a Saudi-led air strike in Yemen's capital Sanaa September 16, 2015. (Photo by Khaled Abdullah/Reuters)





A man holds his son at the site of a Saudi-led air strike in Yemen's capital Sanaa September 16, 2015. (Photo by Khaled Abdullah/Reuters)





Dust rises from the site of a Saudi-led air strike in Yemen's capital Sanaa September 17, 2015. (Photo by Khaled Abdullah/Reuters)





Mahyoub al-Hemiari talks on the phone inside his house which is detroyed by a Saudi-led air strike in Yemen's capital Sanaa,September 17, 2015. At least nine Yemeni civilians were killed in air strikes by Saudi-led warplanes that targeted the home of a leader in the dominant Houthi movement in the capital Sanaa, medical sources said on Thursday. (Photo by Khaled Abdullah/Reuters)





People gather at the site of Saudi-led air strikes in Yemen's capital Sanaa September 17, 2015. (Photo by Khaled Abdullah/Reuters)





Tribesmen loyal to Yemen's government gather outside a local government building in Marib city in this September 17, 2015 file photo. As Gulf Arab troops push through Yemen's central desert into the mountains that lead to the capital held by the Houthis, their Iran-allied foe, winning the hearts and minds of the heavily armed tribes who rule in this area is essential. (Photo by Noah Browning/Reuters)





The feet of a child covered in dust are seen as people search for survivors under the rubble of a house destroyed by an air strike at the old quarter of Yemen's capital Sanaa, September 19, 2015. At least ten Yemeni civilians were killed in air strikes by Saudi-led warplanes that targeted this neighborhood, medical sources said on Saturday. (Photo by Mohamed al-Sayaghi/Reuters)





A man cries as he mourns for his relatives who were killed near a house destroyed by an air strike at the old quarter of Yemen's capital Sanaa, September 19, 2015. (Photo by Mohamed al-Sayaghi/Reuters)





The feet of a child covered in dust are seen as people search for survivors under the rubble of a house destroyed by an air strike at the old quarter of Yemen's capital Sanaa, September 19, 2015. (Photo by Mohamed al-Sayaghi/Reuters)





A man carries a body from the rubble of a house destroyed by an air strike at the old quarter of Yemen's capital Sanaa, September 19, 2015. (Photo by Mohamed al-Sayaghi/Reuters)





People gather at the site of Saudi-led air strikes in Yemen's capital Sanaa September 19, 2015. (Photo by Mohamed al-Sayaghi/Reuters)





A soldier loyal to Yemen's government rides on a tank in the frontline province of Marib, September 19, 2015. (Photo by Reuters/Stringer)





Tribesmen loyal to Yemen's government ride on a pick-up truck in the frontline province of Marib, September 20, 2015. (Photo by Reuters/Stringer)





A soldier loyal to Yemen's government rides on a tank in the frontline province of Marib, September 19, 2015. (Photo by Reuters/Stringer)





Soldiers loyal to Yemen's government ride on an armoured vehicle in the frontline province of Marib, September 20, 2015. (Photo by Reuters/Stringer)





Emirati armoured vehicles are seen on the Yemeni front line province of Marib September 20, 2015. (Photo by Reuters/Stringer)





Soldiers loyal to Yemen's government ride on an armoured vehicle in the frontline province of Marib, September 20, 2015. (Photo by Reuters/Stringer)





A car falls as it is being lifted by a crane at the site of a Saudi-led air strike in Yemen's capital Sanaa September 21, 2015. More than 4,500 Yemeni have been killed since the Saudi-led alliance began military operations in March, in what they said was an attempt to stop the Iranian-allied Houthi group from expanding in Yemen and to restore President Abd-Rabbu Mansour Hadi, who had been pushed into exile in Saudi Arabia. (Photo by Khaled Abdullah/Reuters)





People gather at the site of a Saudi-led air strike in Yemen's capital Sanaa September 21, 2015. (Photo by Khaled Abdullah/Reuters)





People gather at the site of a Saudi-led air strike in Yemen's capital Sanaa September 21, 2015. (Photo by Khaled Abdullah/Reuters)





A man who lost his relatives in a Saudi-led air strike cries at the site of the air strike in Yemen's capital Sanaa September 21, 2015. (Photo by Khaled Abdullah/Reuters)





A car falls as it is being lifted by a crane at the site of a Saudi-led air strike in Yemen's capital Sanaa September 21, 2015. (Photo by Khaled Abdullah/Reuters)





People walk at the site of a Saudi-led air strike in Yemen's capital Sanaa September 21, 2015. (Photo by Khaled Abdullah/Reuters)





Houthi followers wave Yemen's national flag as they ride a van to a ceremony marking the first anniversary of their movement's takeover of the capital Sanaa September 21, 2015. (Photo by Khaled Abdullah/Reuters)





A Houthi follower with fake blood on his clothes lies on the ground to represent a victim as others perform a war dance during a ceremony marking the first anniversary of the Houthi movement's takeover of Yemen's capital Sanaa September 21, 2015. (Photo by Khaled Abdullah/Reuters)





A Houthi follower lies on the ground, resempling a victim, as others perform a war dance during a ceremony marking the first anniversary of the Houthi movement's takeover of Yemen's capital Sanaa September 21, 2015. (Photo by Khaled Abdullah/Reuters)





Houthi miilitants stand guard as people watch a ceremony marking the first anniversary of the Houthi movement's takeover of Yemen's capital Sanaa September 21, 2015. (Photo by Khaled Abdullah/Reuters)





A Houthi follower with fake blood on his clothes lies on the ground to represent a victim as others perform a war dance during a ceremony marking the first anniversary of the Houthi movement's takeover of Yemen's capital Sanaa September 21, 2015. (Photo by Khaled Abdullah/Reuters)





Houthi followers lie on the ground to represent civilian victims of Saudi-led air strikes during a ceremony marking the first anniversary of the Houthi movement's takeover of Yemen's capital Sanaa September 21, 2015. (Photo by Khaled Abdullah/Reuters)





A Houthi militant stands guard as people watch a ceremony marking the first anniversary of the Houthi movement's takeover of Yemen's capital Sanaa September 21, 2015. (Photo by Khaled Abdullah/Reuters)





Houthi followers perform a war dance during a ceremony marking the first anniversary of the Houthi movement's takeover of Yemen's capital Sanaa September 21, 2015. (Photo by Khaled Abdullah/Reuters)





Houthi followers perform a war dance during a ceremony marking the first anniversary of the Houthi movement's takeover of Yemen's capital Sanaa September 21, 2015. (Photo by Khaled Abdullah/Reuters)