ADEN- Houthi forces fought battles street by street with local militia in the old centre of Aden today, as the first boatloads of emergency medical aid arrived to the south Yemeni port city which aid workers say faces a humanitarian catastrophe.

Residents saw a dozen bodies strewn on the streets and said several buildings were burnt or demolished by rocket fire. Mosques broadcast appeals for jihad against the Houthis, Iran-allied fighters who have taken over large areas of Yemen.

By mid-afternoon residents of the central Crater neighborhood said the Houthi push, backed by tanks and armoured vehicles, had been at least partially repelled, and that Houthi fighters had been cleared from some northern neighborhoods.

Iran, which denies arming the Houthis, has condemned the Saudi-led offensive. It sent two warships to the Gulf of Aden on Wednesday, saying they would protect Iranian shipping.

Aden has been the target of a three-week-old assault by the Muslim Shi'ite fighters, who control the capital Sanaa. Their assault prompted Tehran's regional rival Saudi Arabia and its allies to launch air strikes against the Houthis.

The fighting has had a devastating impact on parts of Aden. Scores of people have been killed, water and electricity have been cut off in central neighborhoods, and hospitals have struggled to cope with the casualties.

"It's nearly catastrophic," said the International Committee of the Red Cross spokeswoman in Yemen, Marie Claire Feghali.

"Shops are closed, so people cannot get food, they cannot get water. There are still dead bodies in the street. Hospitals are extremely exhausted."