UN aid chief Mark Lowcock has warned that Yemen is "on the brink of a major catastrophe," as the world body pushes for peace talks in the impoverished and war-wracked country.

His comments on Saturday came after renewed deadly clashes between Houthi rebels and pro-government forces in the Red Sea port city of Hodeidah, vital for the flow of humanitarian aid.

Wrapping up his trip, Lowcock said conditions had deteriorated alarmingly since his last visit in October 2017.

"In Aden, I met emaciated children so malnourished they could barely open their eyes," Lowcock said in a statement.

"Humanitarian assistance helps many of these children recover. But I also heard heartbreaking stories of children relapsing again and again because their families simply can't afford food or proper medical care."

The United Nations has termed Yemen the world's worst humanitarian crisis.

Lowcock reiterated the organisation's readiness to play a role to ensure that the rebel-held Hodeidah port, a key entry point for imports and aid, can remain open.

Under heavy international pressure, Saudi-backed pro-government forces have largely suspended an offensive launched in June to take the port city.

Sporadic clashes have, however, continued since a fragile truce began on 13 November.

Peace talks face 'setbacks'

Fighting on Friday in the east and south of Hodeidah left 10 fighters dead, an official and medical sources told the AFP news agency on Saturday.

Medical sources confirmed the bodies of eight rebels had been transferred to hospitals and that two fighters with pro-government forces were also killed.

Intermittent clashes continued on Saturday, Hodeidah residents told AFP by phone.

Saudi Arabia accused the Houthis of launching a "military projectile" across the border on Friday, saying it hit a house and injured two people in the kingdom, the official SPA news agency reported.

The violence follows a visit to Hodeidah last month by UN envoy Martin Griffiths to press for peace talks.

The proposed discussions have been backed by both the rebels and the Saudi-led government and were expected to take place in Sweden next week.

UN Secretary-General Antonio Guterres, however, has played down the early December schedule and said he hoped talks would start "this year".

"But, as you know, there have been some setbacks," he said on Thursday.

Previous talks planned for September in Geneva failed to get underway as the Houthi delegation never left Yemen's rebel-held capital Sanaa, arguing that the UN could not guarantee their safe return.

Lowcock said it was "not too late" to pull Yemen back from the brink but warned that more resources were needed.

"Yemen is the world’s largest humanitarian operation, but in 2019 it will need to be substantially bigger," he said.

Donors this year have provided $2.3bn for the 2018 response plan, or about 80 per cent of requirements, he added.

According to UN figures, nearly 10,000 people have been killed since the Saudi-led coalition joined the conflict in 2015 to bolster the government against the Houthis.

UN agencies say that 14 million people are at risk of starvation in Yemen.