The US has warned Yemen’s Houthi rebels to avoid seeking revenge and risking an escalation in the conflict after six children and 16 people overall were killed in a Saudi coalition air strike.

Monday’s attack on the vital Houthi-controlled port of Hodeida was condemned by the United Nations as “one of the deadliest attacks on children” in the entire civil war, which has just entered its fourth year.

“We take this report very seriously and it will be fully investigated as all reports of this nature are - using an internationally approved, independent process,” a spokesperson for the Saudi-led coalition supporting Yemen’s exiled government said.

Devastation on the ground in Yemen displayed by International Rescue Committee in shocking video

Rebel factions retaliated with an attack on a Saudi oil tanker in the Red Sea on Tuesday, causing “minor damage” to the ship, the Saudi coalition said. The attack occurred in international waters.

White House press secretary Sarah Huckabee Sanders said in a statement Wednesday that the US is “very concerned about the Houthis' latest attempt to escalate the war in Yemen.”

“We call on the Houthis to cease further escalation and demonstrate their commitment to a peace process by engaging in constructive dialogue,” she added.

The situation in Yemen Show all 14 1 /14 The situation in Yemen The situation in Yemen Houthi supporters trample on a US flag during a gathering mobilizing more fighters into several Yemeni battlefronts, in Sana'a, Yemen EPA The situation in Yemen People carry the coffins of men, who were killed in the recent Saudi-led airstrikes during their funeral, in the Old City of Sanaa, Yemen AP The situation in Yemen Pro-government fighters give food to Yemeni children on the road leading to the southwestern port city of Mokha. Yemeni rebels are putting up fierce resistance in a key Red Sea port city where they are encircled by pro-government force Getty Images The situation in Yemen A Yemeni stands in front of a graffiti protesting US military operations in war-affected Yemen, in Sana'a, Yemen. According to reports, US Special Forces troops allegedly disembarked from US helicopters in the Yemeni town of Yakla and attacked several houses belonging to members of the terrorist group Al-Qaeda, killing three high-ranking Al-Qaeda members and nine civilians, six women and three children. One American serviceman has been killed and three injured in the attack EPA The situation in Yemen US Special Forces troops allegedly disembarked from US helicopters in the Yemeni town of Yakla and attacked several houses belonging to members of the terrorist group Al-Qaeda, killing three high-ranking Al-Qaeda members and nine civilians, six women and three children. One American serviceman has been killed and three injured in the attack EPA The situation in Yemen A Yemeni female fighter supporting the Shiite Huthi rebels, and carrying weapons used for ceremonial purposes, takes part in an anti-Saudi rally in the capital Sanaa Getty Images The situation in Yemen Yemeni female fighters supporting the Shiite Huthi rebels, and carrying weapons used for ceremonial purposes, take part in an anti-Saudi rally in the capital Sanaa Getty Images The situation in Yemen A boy shouts slogans next to pro-Houthi fighters, who have been injured during recent fighting, during a rally held to honour those injured or maimed while fighting in Houthi ranks in Sanaa, Yemen Reuters The situation in Yemen Balls of fire and smoke rise from a Houthi-held military camp following alleged Saudi-led airstrikes, in Sana'a, Yemen EPA The situation in Yemen Yemenis search under the rubble of damaged houses following reported Saudi-led coalition air strikes on the outskirts of the Yemeni capital Sanaa Getty Images The situation in Yemen A Yemeni boy looks on as Yemenis search under the rubble of damaged houses following reported Saudi-led coalition air strikes on the outskirts of the Yemeni capital Sanaa Getty The situation in Yemen A Yemeni boy sits amidst the rubble of damaged houses following reported Saudi-led coalition air strikes on the outskirts of the Yemeni capital Sanaa AFP/Getty The situation in Yemen Marine One with US President Donald Trump flies with a decoy and support helicopters to Dover Air Force Base in Dover, Delaware, for the dignified transfer of Navy Seal Chief Petty Officer William 'Ryan' Owens who was killed in Yemen Getty Images The situation in Yemen US President Donald Trump aboard the Marine One to greet the remains of a US military commando killed during a raid on the al Qaeda militant group in southern Yemen on Sunday, at Dover Air Force Base, Delaware, US Reuters

Yemen slipped into full-blown civil war in March 2015 after neighbouring Riyadh led a coalition of Arab states in a bombing campaign designed to oust Iran-backed Shia Houthi rebels from the capital of Sanaa.

It has since descended into the worst humanitarian crisis in the world, with two thirds of the 28-million-strong population dependent on aid, eight million living on the brink of famine and the worst outbreak of cholera in modern history.

The disaster has to a large degree been caused by Saudi blockades of Houthi controlled ports and airspace, strangling imports of food and medicine.

Yemen: More than 50,000 children expected to die of starvation and disease by end of year

International donors promised more than $2bn (£1.4bn) in humanitarian aid for Yemen at a pledging conference in Geneva on Tuesday.

The amount, however, fell well short of the appeal for $2.96bn (£2.1bn) in emergency funding to stop the country collapsing completely in 2018.