Saudi-led warplanes launched a fresh wave of air strikes across Yemen targeting Iran-backed rebels as fighting raged on the ground in the south of the country, witnesses said.

The air raids pounded arms depots under the control of the Shiite Huthi rebels in the locality of Ghula yesterday, in Omran province north of Sanaa, residents said.

They followed similar bombardments of weapons storage facilities in the capital that sparked deadly explosions, and strikes on the Dhabwa military base, which is currently under rebel control.

In the western province of Hodeida, a military airport was twice bombed by coalition warplanes, according to residents.

The Arab coalition has stepped up raids on positions held by the Huthis and their allies since a humanitarian ceasefire ended late on Tuesday.

At Hajja in the north of the country, a gathering of Huthis was struck, killing at least 12 of the Shiite fighters, witnesses reported.

Air strikes also attacked rebel positions in Dhamar, officials there said, while tank and mortar fire sounded across some sectors of the central region where heavy fighting took place, according to tribal sources.

In southern Yemen, warplanes targeted rebels locked in combat with tribesmen in Ataq, the capital of Shabwa province, military officials said.

The fighting killed at least 28 people, including 17 Huthis and 11 tribesmen, the sources said.

In Aden, clashes raged in the north, east and west of the port city between rebels and fighters loyal to President Abedrabbo Mansour Hadi, military sources said.

The Saudi-led coalition launched the air campaign against the Huthis on March 26 after the rebels seized the capital and advanced on Hadi's stronghold of Aden, forcing him to flee to Riyadh.

The United Nations, which plans to hold a conference on Yemen in Geneva next week, says the violence has killed more than 1,000 people and displaced close to half a million more.