Saudi-led air strikes have killed 28 Houthi rebels south of the port of Hodeida on Yemen's west coast, medics and security sources close to the insurgents said on Friday.

The reports came as the Uited Nations refugee agency UNHCR warned of a new displacement of civilians in the area.

The security sources said the air strikes on Thursday and Friday hit five towns controlled by the Houthis around 70 kilometres south of Hodeida.

Medical sources said 28 Houthis were killed and 17 others wounded in the strikes.

There has been no let-up in the air campaign against the rebels that a Saudi-led coalition has been waging since March 2015.

The air strikes have intensified since the December 4 killing of ex-president Ali Abdullah Saleh at the hands of the Houthis after his alliance with the rebels collapsed.

At the same time forces of the Yemeni government have stepped up attacks on the rebels and last week retook the Red Sea town of Khokha from the Houthis.

The security sources said new clashes broke out on Friday as government forces tried to push towards Hodeida.

UNHCR said it was “bracing for further displacement and a spike in humanitarian needs as hostilities intensify in frontline areas on Yemen's west coast”.

Hodeida is the main conduit for UN-supervised deliveries of food and medicine but the rebel-held port is controlled by the Houthis and remains closed, forcing the UN to divert aid supplies to other areas.

“To date we have deployed emergency relief items for 2,000 families in Hodeida, and a further 2,000 aid kits are on their way along with 2,000 emergency shelter kits,” the UNHCR said in a statement.

“As the port of Hodeida remains closed an additional 43 containers with emergency, shelter and household aid, including plastic tarpaulins and blankets for more than 20,000 families, had to be diverted to Aden,” it added.

More than 2,000 people have died of cholera in Yemen this year, adding to the 8,600 killed in the conflict between the Saudi-backed government and rebels since 2015.