The provincial government official, who spoke on condition of anonymity, blamed Houthi rebels who control several neighborhoods in Yemen’s second city for not allowing the ship to dock at Aden’s port, which is controlled by pro-government fighters.

“The Huthis fired shells at a ship chartered by the U.N. that was carrying 7,000 tons of food… when it was within a nautical mile of Aden’s port,” the official said, adding that the vessel itself was not hit.

“The ship was forced to turn back and by night time it was about five to eight nautical miles from Aden,” he added.

According to the official, the vessel had set off from Djibouti, which the U.N. uses as a hub for humanitarian aid bound for Yemen.

The incident was confirmed by a port official, who also declined to be identified.

“The Houthi fire forced the ship to turn back as it approached the port,” the port official said.

He accused the rebels of “imposing a food blockade on areas of Aden under the control of the Popular Resistance Committees”, which are a collection of pro-government fighters, Sunni tribes and southern separatists.

Saudi Arabia has been leading an air war since March 26 targeting Iran-backed militia in Yemen and allied forces loyal to former leader Ali Abdullah Saleh, in an effort to restore U.N.-backed President Abdrabbu Mansour Hadi to power.

Clashes have also raged on the ground between the rebels, who seized the capital Sanaa last year, and local militia fighting their advance, especially in southern Yemen.

The Yemen conflict has killed almost 2,000 people and wounded 8,000, according to the World Health Organization.