A girl sits inside her house which was damaged by a shell which landed from a nearby missile base after the base was struck by a Saudi-led coalition air strike, near Sanaa April 23, 2015. REUTERS/Mohamed al-Sayaghi 

A woman cries after her home was damaged by a shell which landed from a nearby missile base after the base was struck by a Saudi-led coalition air strike, near Sanaa April 23, 2015. REUTERS/Mohamed al-Sayaghi 

A girl drinks water from a faucet amid an acute shortage of clean drinking water in Sanaa, April 24, 2015. REUTERS/Mohamed al-Sayaghi 

A worker throws a stuffed toy to another as they move furniture from a house damaged after an air strike by a Saudi-led coalition struck a nearby missile base, in Yemen's capital Sanaa April 23, 2015. REUTERS/Khaled Abdullah 

A man looks at his home which was damaged by a shell which landed from a nearby missile base after the base was struck by a Saudi-led coalition air strike, near Sanaa April 23, 2015. REUTERS/Mohamed al-Sayaghi 

A boy holds a blood-stained garment at the site of an air strike on a house, in Bait Rejal village west of Yemen's capital Sanaa April 7, 2015. The strike killed three women and three children from one family on Tuesday, local media reported. REUTERS/Khaled Abdullah 

A boy pulls containers of water after he filled them at a faucet, amid an acute shortage of clean drinking water in Sanaa, April 20, 2015. REUTERS/Mohamed al-Sayaghi 

Children ride on the back of a pick-up truck with their luggage as they flee Saudi-led air strikes in Sanaa April 6, 2015. Foreign nationals were on their way out of Yemen on Monday as 12 days of strikes by a Saudi-led coalition have failed to halt the advance of the Iran-allied Houthis and triggered a growing humanitarian crisis for residents in central districts now cut off from the mainland. REUTERS/Khaled Abdullah 

A man looks at damage in his house caused by an April 20 air strike that hit a nearby army weapons depot in Sanaa April 21, 2015. REUTERS/Mohamed al-Sayaghi 

A boy looks at the bloodstains on a vehicle which was used to transport victims near 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 

A man reacts at the site of an air strike in Sanaa April 8, 2015. A Saudi-led coalition air strike hit an office of Yemen's Houthi rebels near the pro-Houthi television channel al-Maseera in central Sanaa on Wednesday, witnesses said. REUTERS/Khaled Abdullah 

A man walks past a car damaged by an air strike on Monday which hit a nearby army weapons depot, in Sanaa April 21, 2015. REUTERS/Mohamed al-Sayaghi 

A girl sits in front of her mothr sleeping on the sidewalk in a street in Sanaa April 11, 2015. The humanitarian situation is witnessing a marked deterioration, a result of the war waged by the Saudi-led coalition forces According to media. REUTERS/Mohamed al-Sayaghi 

Children stand next to a shell which landed on their house from a nearby missile base after the base was struck by a Saudi-led coalition air strike, near Sanaa April 23, 2015. REUTERS/Mohamed al-Sayaghi 

A man stands in a room of a house burnt after an air strike by a Saudi-led coalition struck a nearby missile base, in Yemen's capital Sanaa April 23, 2015. REUTERS/Khaled Abdullah 

A boy cries near 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 

A boy carries jerrycans to fill with water from a faucet amid an acute shortage of clean drinking water in Sanaa April 20, 2015. REUTERS/Mohamed al-Sayaghi 

A boy looks through a window of his home damaged by an air strike near Sanaa Airport March 31, 2015. Air raids by a Saudi-led coalition again hit Houthi militia targets across Yemen on Monday night, striking the group's northern stronghold of Saadeh, the capital, Sanaa, and the central town of Yarim, residents and media said. REUTERS/Khaled Abdullah 

A boy searches for food amongst litter on a streetside in Sanaa April 8, 2015. REUTERS/Mohamed al-Sayaghi 

A boy transports containers of water at a private well as people store water, amid shortage of clean drinking water, in Sanaa April 8, 2015. REUTERS/Mohamed al-Sayaghi