Civilians were killed in western Yemen on Thursday in a missile strike for which the Houthi rebels and a Saudi-led coalition fighting them traded blame.

The rebel-run Saba news agency said women and children were among at least 31 people killed or wounded in an air strike that hit a bus and a home in the Al-Durayhimi district, south of the strategic port city of Hodeida.

Youssef al-Hadiri, spokesman of the health ministry which is under the control of the Iranian-backed Houthi rebels, earlier told dpa that airstrikes hit the region of Alkoui and targeted a vehicle which was carrying civilians trying to escape the area.

Al Hadiri said among the killed were 20 children, five women and the driver.

According to al Haderi, the victims were trying to escape Alkoui area after a raid targeted a house in the area on Wednesday night killing four civilians and wounding two others.

Meanwhile, Mark Lowcock, the UN undersecretary-general for humanitarian affairs said at least 22 children and four women were killed by a Saudi-led coalition air strike while fleeing fighting in Yemen, condemning attacks on civilians.

Local residents in the area confirmed to dpa that all the fatalities were civilians.

But the United Arab Emirates, a key partner in the Saudi-led coalition, said the Houthis launched a "ballistic (missile) made in Iran".

A child was killed and dozens of others were wounded, three of them seriously, according to Emirati state news agency WAM.

It was not immediately possible to independently verify the accounts given by the two sides.

The Al-Durayhimi area lies some 20 kilometers (12 miles) south of Hodeida, and has seen two weeks of fighting between the rebels and pro-government forces backed by the UAE.

But the wider offensive to retake Hodeida from the Houthis has been halted pending the outcome of negotiations, the coalition has said.

Yemeni forces have since seized Hodeida's airport and are seeking to retake the city and its vital port, through which an estimated 80 percent of imports and aid reach Yemen.

Aid agencies have warned that the offensive could have devastating consequences for the population, which is already on the brink of famine.

The latest civilian deaths comes after 40 children and 11 adults were killed in an attack in northern Yemen earlier this month.

The August 9 air strike sparked international condemnation and the Saudi-led coalition announced an investigation.

The coalition has been accused of causing numerous civilian casualties in the civil war in Yemen.

It has admitted a small number of mistakes, but accuses the Houthis of routinely using civilians as human shields.

A report published by Human Rights Watch on Friday said the coalition's investigations into alleged war crimes "have lacked credibility".

"For more than two years, the coalition has claimed that (its investigative body) JIAT was credibly investigating allegedly unlawful air strikes, but the investigators were doing little more than covering up war crimes," HRW's Middle East director, Sarah Leah Whitson, said in a statement.

The coalition led by Saudi Arabia intervened in support of President Abedrabbo Mansour Hadi as he fled into exile in the face of a rebel offensive in 2015.

It has recaptured most of the south and stretches of the Red Sea coast but the capital Sanaa and much of the north remain in the hands of the rebels.

The conflict has killed nearly 10,000 people and triggered what the United Nations has described as the world's worst humanitarian crisis.

Meanwhile, the Saudi-led coalition said late Thursday that it foiled an attack involving an explosives-laden boat on the shores of Hodeida that had been planned by Houthi rebels, the Saudi-owned television Al Arabiya reported.

The broadcaster quoted a coalition statement saying that the Houthi militia and Iranian Revolutionary Guards "continue to threaten international shipping routes and international trade."

It added that the alliance had taken the necessary measures "to protect commercial vessels of the alliance."

Dubai-based Al Arabiya broadcast a video of the speedboat, allegedly loaded with explosives.

Pro-Houthi broadcaster al-Masirah, meanwhile, said its naval forces carried out a special operation.

It added that the special operation inside the Saudi waters "hit its target accurately."