Smoke billows from a burning fuel truck after it was set ablaze during clashes between Houthis and fighters of the Popular Resistance Committees in Yemen's southwestern city of Taiz May 25, 2015. Picture taken May 25, 2015. REUTERS/Stringer TPX IMAGES OF THE DAY

ATTENTION EDITORS - VISUAL COVERAGE OF SCENES OF INJURY OR DEATH

A medic attends to people injured by a mortar shell blast during clashes between Houthis and fighters of the Popular Resistance Committees in Yemen's southwestern city of Taiz May 26, 2015. REUTERS/Stringer

TPX IMAGES OF THE DAY

A man comforts another, whose brother was killed by a mortar shell blast during clashes between Houthis and fighters of the Popular Resistance Committees in Yemen's southwestern city of Taiz May 26, 2015. REUTERS/Stringer 

People try to put out a burning fuel truck after it was set ablaze during clashes between Houthis and fighters of the Popular Resistance Committees in Yemen's southwestern city of Taiz May 25, 2015. Picture taken May 25, 2015. REUTERS/Stringer TPX IMAGES OF THE DAY

A man injured by a mortar shell blast during clashes between Houthis and fighters of the Popular Resistance Committees is rushed to a hospital in Yemen's southwestern city of Taiz May 26, 2015. REUTERS/Stringer 

A woman injured by a mortar shell blast during clashes between Houthis and fighters of the Popular Resistance Committees lies on a hospital bed in Yemen's southwestern city of Taiz May 26, 2015. REUTERS/Stringer 

A man comforts another, whose brother was killed by a mortar shell blast during clashes between Houthis and fighters of the Popular Resistance Committees in Yemen's southwestern city of Taiz May 26, 2015. REUTERS/Stringer 

People look at the remains of a car that caught fire after a fuel truck was set ablaze during clashes between Houthis and fighters of the Popular Resistance Committees in Yemen's southwestern city of Taiz May 25, 2015. According to local media, nine people were killed and many injured as the victims were queuing up beside the fuel truck to fill up their jerrycans with petrol before it was set ablaze. Picture taken May 25, 2015. REUTERS/Stringer 

The burnt interior of a house is seen after a fuel truck was set ablaze in front of the house during clashes between Houthis and fighters of the Popular Resistance Committees in Yemen's southwestern city of Taiz May 25, 2015. Picture taken May 25, 2015. According to local media, nine people were killed and many injured as the victims were queuing up beside the fuel truck to fill up their jerrycans with petrol before it was set ablaze. REUTERS/Stringer 

People gather at the site a fire afte a fuel truck was set ablaze during clashes between Houthis and fighters of the Popular Resistance Committees in Yemen's southwestern city of Taiz May 25, 2015. According to local media, nine people were killed and many injured as the victims were queuing up beside the fuel truck to fill up their jerrycans with petrol before it was set ablaze. Picture taken May 25, 2015. REUTERS/Stringer TPX IMAGES OF THE DAY