The United Nations warned Thursday that thousands of Yemeni civilians were at risk in the western province of Hodeida after an increase in military clashes this month.

Since 2014, Yemen has been engulfed in a war between the internationally recognised government -- supported by a Saudi-led military coalition -- and the Iran-backed Huthi rebels that has triggered a devastating humanitarian crisis.

The latest clashes in the rebel-held Red Sea port city of Hodeida -- the main gateway for food, fuel and humanitarian aid to the rest of the country -- are the most violent since a truce negotiated in the area by the United Nations came into force in 2018.

The UN Office for the Coordination of Humanitarian Affairs (OCHA) said in a statement that "concern is increasing" with "thousands of civilians at risk". 

It added that preliminary reports showed that at least 700 people has been displaced by the recent fighting and that "there have already been civilian casualties".

At least eight civilians, mostly women and children, were killed last week, and many houses and farms damaged, the UN said.

"Indiscriminate attacks on residential areas are a breach of international humanitarian law and must stop immediately," said Auke Lootsma, the UN's humanitarian coordinator in Yemen. 

Two explosions rattled Hodeida city on Wednesday night, residents told AFP. 

The Huthis have attacked to the south of the city where pro-government forces maintain positions, pro-government military sources said earlier this month.

On January 18, military sources said that some 150 Yemeni pro-government soldiers and Huthi rebels had been killed in a week of fighting.

A Yemeni military source said Thursday that fighting between the warring sides has subsided slightly since then but that "intermittent clashes" were ongoing. 

"The parties must remember that they have a duty to take all necessary measures to protect civilians at all times and allow humanitarians to respond to the injured and displaced," the UN said.