The UN envoy for Yemen arrived in the rebel-held capital Sanaa on Saturday for emergency talks on the key aid port of Hodeida where rebel fighters are battling a regional coalition.

Martin Griffiths is expected to propose to rebel leaders that they cede control of the Red Sea port to a UN-supervised committee to avoid further fighting with advancing government troops which are backed by Saudi Arabia and the United Arab Emirates.

He did not speak to reporters on his arrival at Sanaa international airport.

More than 70 percent of Yemeni imports pass through Hodeida's docks and the fighting has raised UN fears of humanitarian catastrophe in a country already teetering on the brink of famine.

The Yemeni government and it allies launched their offensive on Wednesday. At least 139 combatants have already been killed, according to medical and military sources.

The rebels have controlled the Hodeida region with its population of some 600,000 people since 2014.

Earlier this year, the Saudi-led coalition imposed a near-total blockade on the city's port alleging that it was being used as a conduit for arms smuggling to the rebels by its regional arch rival Iran.

The capture of Hodeida would be the coalition's biggest victory of the war so far and on Thursday rebel leader Abdel Malek Al-Huthi called on his forces to put up fierce resistance and turn the region into a quagmire for coalition troops.

Hodeida airport

The Yemeni army on Saturday claimed it had seized control of the rebel base at Hodeida's disused airport, which has been closed since 2014.

An AFP correspondent on the front line could not confirm the news.

A spokesman for the coalition, which has ground troops taking part in the Hodeida offensive, did not respond to repeated requests for comment.

There was no immediate word from the rebels.

The army had said on Friday it was two kilometres (little more than a mile) from the airport, which lies to the south of the vital docks.

The United Nations and relief organisations have warned that any all-out assault on the city would put hundreds of thousands of people at risk.

The fighting is already nearing densely populated residential areas, the Norwegian Refugee Council warned, and aid distributions have been suspended in the west of the city.

The International Committee of the Red Cross said thousands were likely to flee if the fighting continued.

On Thursday, the UN Security Council demanded that Hodeida port be kept open to vital food shipments but stopped short of backing a Swedish call for a pause in the Saudi-backed offensive to allow for talks on a rebel withdrawal.

The Yemen war has claimed some 10,000 lives since the coalition intervened in 2015 when President Abedrabbo Mansour Hadi fled into exile when the rebels overran much of the country.

More than 22 million Yemenis are in need of aid, including 8.4 million who are at risk of starvation, according to the UN, which has described the conflict as the world's worst humanitarian crisis.