Iraqi security forces' vehicles are seen in the city of Ramadi, January 2, 2016. Picture taken January 2, 2016. (Photo by Reuters/Stringer)





A fighter of the pro-government Popular Resistance Committees stands guard near an entrance of Yemen's southwestern city of Taiz, January 3, 2016. (Photo by Reuters/Stringer)





A member of the Iraqi security forces runs after planting an Iraqi flag in the ground, in the city of Ramadi, January 2, 2016. Picture taken January 2, 2016. (Photo by Reuters/Stringer)





A fighter of the pro-government Popular Resistance Committees stands guard near an entrance of Yemen's southwestern city of Taiz, January 3, 2016. (Photo by Reuters/Stringer)





Fighters of the pro-government Popular Resistance Committees take positions as they guard an entrance of Yemen's southwestern city of Taiz, January 3, 2016. (Photo by Reuters/Stringer)





A man walks past a damaged water tanker truck at the site of a Saudi-led air strike in Yemen's capital Sanaa January 4, 2016. (Photo by Khaled Abdullah/Reuters)





People walk next to a damaged building at the site of a Saudi-led air strike in Yemen's capital Sanaa January 4, 2016. (Photo by Khaled Abdullah/Reuters)





A vendor steps out of his shop damaged by a Saudi-led air strike in Yemen's capital Sanaa January 4, 2016. (Photo by Khaled Abdullah/Reuters)





Iraqi security forces and pro-government Sunni tribal fighters carry the body of a woman killed in Ramadi city, Iraq January 4, 2016. (Photo by Reuters/Stringer)





A fighter of the pro-government Popular Resistance Committees, is being carried on a blanket after he was injured during clashes with Houthi fighters in Yemen's southwestern city of Taiz, January 5, 2016. (Photo by Reuters/Stringer)





Iraqi security forces and pro-government Sunni tribal fighters evacuate a badly injured man in Ramadi city, Iraq January 4, 2016. (Photo by Reuters/Stringer)





Bodies of Houthi fighters, killed during clashes with pro-government Popular Resistance Committees fighters, are seen in a building in Yemen's southwestern city of Taiz, January 5, 2016. (Photo by Reuters/Stringer)





People gather at the site of a car bomb attack in Yemen's southern port city of Aden January 5, 2016. Three senior southern Yemeni officials survived a suicide car bomb attack on their convoy in Aden and a subsequent gun battle that killed three of their guards on Tuesday, a government spokesman and security sources said. (Photo by Nasser Awad/Reuters)





A man looks at a damaged car at the site of a car bomb attack in Yemen's southern port city of Aden January 5, 2016. (Photo by Nasser Awad/Reuters)





People gather at the site of a Saudi-led air strike in Yemen's capital Sanaa January 6, 2016. (Photo by Khaled Abdullah/Reuters)





People carry furniture from their house after it was hit by a Saudi-led air strike in Yemen's capital Sanaa January 6, 2016. (Photo by Khaled Abdullah/Reuters)





People stand at the site of a Saudi-led air strike in Yemen's capital Sanaa January 6, 2016. (Photo by Khaled Abdullah/Reuters)





Supporters of the Houthi movement protest against the execution of Shi'ite Muslim cleric Nimr al-Nimr in Saudi Arabia, during a demonstration outside the Saudi embassy in Sanaa, Yemen January 7, 2016. (Photo by Khaled Abdullah/Reuters)





Supporters of the Houthi movement protest against the execution of Shi'ite Muslim cleric Nimr al-Nimr in Saudi Arabia, during a demonstration outside the Saudi embassy in Sanaa, Yemen January 7, 2016. The posters read: "Martyr Sheikh Nimr al-Nimr". (Photo by Khaled Abdullah/Reuters)





A fighter of the Southern Resistance Committees fires a machine gun mounted on a pick-up truck during fighting against Houthi fighters in Karish of Yemen's southern province of Lahej January 7, 2016. (Photo by Reuters/Stringer)





A Houthi fighter lies on the ground after he was taken prisoner by pro-government Popular Resistance Committees in Yemen's southwestern city of Taiz January 7, 2016. (Photo by Reuters/Stringer)





Houthi supporters demonstrate against Saudi-led air strikes in Yemen's capital Sanaa January 8, 2016. (Photo by Khaled Abdullah/Reuters)





A Houthi militant stands guard as Houthi supporters demonstrate against Saudi-led air strikes in Yemen's capital Sanaa January 8, 2016. (Photo by Khaled Abdullah/Reuters)





Houthi supporters demonstrate against Saudi-led air strikes in Yemen's capital Sanaa January 8, 2016. (Photo by Khaled Abdullah/Reuters)





Houthi supporters demonstrate against Saudi-led air strikes in Yemen's capital Sanaa January 8, 2016. (Photo by Khaled Abdullah/Reuters)





Tribal fighters loyal to Yemen's government and children pose for a picture in Al Khurais village of Nihm district east of the capital Sanaa January 11, 2016. (Photo by Ali Owidha/Reuters)





A soldier and tribal fighters loyal to Yemen's government are pictured at their position in Al Khurais village of Nihm district east of the capital Sanaa January 11, 2016. (Photo by Ali Owidha/Reuters)





Tribal fighters loyal to Yemen's government ride in the back of a pick-up truck in Al Khurais village of Nihm district east of the capital Sanaa January 11, 2016. (Photo by Ali Owidha/Reuters)





A tribal fighter loyal to Yemen's government stands in Al Khurais village of Nihm district east of the capital Sanaa January 11, 2016. (Photo by Ali Owidha/Reuters)





A girl and a boy wait to fill jerrycans with water at a public tap in Al Khurais village of Nihm district east of the capital Sanaa January 11, 2016. (Photo by Ali Owidha/Reuters)





A girl looks as she stands outside her home in Al Khurais village of Nihm district east of the capital Sanaa January 11, 2016. (Photo by Ali Owidha/Reuters)





A tribal fighter loyal to Yemen's government poses for a picture in Al Khurais village of Nihm district east of the capital Sanaa January 11, 2016. (Photo by Ali Owidha/Reuters)





A tribal fighter loyal to Yemen's government stands outside a house in Al Khurais village of Nihm district east of the capital Sanaa January 11, 2016. (Photo by Ali Owidha/Reuters)





A boy pauses as he walks in Al Khurais village of Nihm district east of the capital Sanaa January 11, 2016. (Photo by Ali Owidha/Reuters)





Men gather at the site of a house destroyed by Saudi-led airstrikes in Sanaa, Yemen, Friday, January 8, 2016. (Photo by Hani Mohammed/AP Photo)





Fighters loyal to Yemen's President Abedrabbo Mansour Hadi celebrate after they managed to secure completely and take control of the port of the southern city of Aden, on January 4, 2016. Authorities in Aden imposed a curfew after fierce battles in the port of Aden that killed 17 people, among them nine members of the security forces including a colonel, the security sources said. (Photo by Saleh Al-Obeidi/AFP Photo)