(AFP) - US and British forces struck rebel-held Yemen early on Friday after weeks of disruptive attacks on Red Sea shipping by the Iran-backed Huthis who say they act in solidarity with Gaza.

The pre-dawn air strikes add to escalating fears of wider conflict in the region, where violence involving Tehran-aligned groups in Yemen as well as Lebanon, Iraq and Syria has surged since the Israel-Hamas was began in early October.

Iran "strongly condemned" the strikes, which the United States, Britain and eight other allies said aimed to "de-escalate tensions".

China said it was "concerned about the escalation of tensions in the Red Sea", and news of the strikes sent oil prices up more than two percent.

The Huthis have carried out a growing number of attacks on what they deem to be Israeli-linked shipping in the key international trade route since October 7, when Hamas's unprecedented attack on Israel sparked the war which is still raging in the besieged Gaza Strip.

The rebels have controlled a major part of Yemen since a civil war erupted there in 2014 and are part of a regional Iran-backed "axis of resistance" against Israel and its allies.

Friday's strikes targeted an airbase, airports and a military camp, the Huthis' Al-Masirah TV station said, with AFP correspondents and witnesses reporting they could hear heavy strikes in Hodeida and Sanaa.

"Our country was subjected to a massive aggressive attack by American and British ships, submarines and warplanes," said Hussein al-Ezzi, the rebels' deputy foreign minister.

"America and Britain will have to prepare to pay a heavy price and bear all the dire consequences of this blatant aggression," he added according to official Huthi media.

US President Joe Biden called the strikes a "defensive action" after the Red Sea attacks and said he "will not hesitate" to order further military action if needed.

With fighter jets and Tomahawk missiles, 60 targets at 16 Huthi locations were hit by more than 100 precision-guided munitions, US Central Command said in a statement.

Unverified images on social media, some of them purportedly of Al-Dailami airbase north of the rebel-held capital Sanaa, showed explosions lighting up the sky as loud bangs and the roar of planes sounded.

Huthi military spokesman Yahya Saree said at least five people had been killed.

- 'Repeated warnings' -

Nasser Kanani, spokesman for Iran's foreign ministry, said that the Western strikes "will have no result other than fuelling insecurity and instability in the region", while "diverting the world's attention" from Gaza.

In a statement, Biden called the strikes a success and said he ordered them "against a number of targets in Yemen used by Huthi rebels to endanger freedom of navigation in one of the world's most vital waterways."

Biden called the strikes a "direct response" to the "unprecedented" attacks by the Huthis which included "the use of anti-ship ballistic missiles for the first time in history".

Blaming the Huthis for ignoring "repeated warnings", British Prime Minister Rishi Sunak said in a statement the strikes were "necessary and proportionate".

Britain's defence ministry released footage of Royal Air Force jets returning to their Cyprus base after the mission, and US Centcom video showed warplanes apparently taking off from a sea-based carrier.

US Defence Secretary Lloyd Austin said the strikes "targeted sites associated with the Huthis' unmanned aerial vehicle, ballistic and cruise missile, and coastal radar and air surveillance capabilities".

A joint statement by the United States, Britain, Australia, Bahrain, Canada, Denmark, Germany, the Netherlands, New Zealand and South Korea said the "aim remains to de-escalate tensions and restore stability in the Red Sea".

The Huthis said they will not be deterred.

"We affirm that there is absolutely no justification for this aggression against Yemen, as there was no threat to international navigation in the Red and Arabian Seas," Huthi spokesman Mohammed Abdulsalam posted on X, formerly Twitter.

He said there was no threat to any vessels apart from "Israeli ships or those heading to the ports of occupied Palestine".

Prior to Friday's strikes, Gerald Feierstein, a former US ambassador to Yemen, said bombing the Huthis would be "counter-productive".

Strikes against the Huthis, who have weathered years of air raids by a Saudi-led coalition, would have little impact and would only raise their standing in the Arab world, said Feierstein of the Middle East Institute think-tank in Washington.

- Saudi call for 'restraint' -

Yemen's neighbour Saudi Arabia is trying to extricate itself from a nine-year war with the Huthis, though fighting has largely been on hold since a truce in early 2022.

"The Kingdom of Saudi Arabia is following with great concern the military operations," a foreign ministry statement said after the US and British strikes.

Riyadh called for "self-restraint and avoiding escalation".

US and allied forces in Iraq and Syria, where they are part of an anti-jihadist coalition, have also faced stepped-up attacks since the outbreak of the war in Gaza, with Washington responding to several by bombing the sites of pro-Iran groups.

Israel has also stepped up strikes against targets in Syria, and has exchanged regular fire with Lebanon's Hezbollah over its northern border.

Washington, which has said it seeks to avoid a spreading conflict, in December announced a maritime security initiative, Operation Prosperity Guardian, to protect shipping in the Red Sea route which normally carries about 12 percent of global maritime trade.

Twelve nations led by the United States warned the Huthis on January 3 of "consequences" unless they immediately stopped attacks on commercial vessels.

On Tuesday, however, the Huthis launched what London called their most significant attack yet, with US and British forces shooting down 18 drones and three missiles.

The final straw for the Western allies appeared to come early Thursday when the US military said the Huthis fired an anti-ship ballistic missile into a shipping lane in the Gulf of Aden.

It was the 27th attack on international shipping in the Red Sea since November 19, the US military said.

The intensifying attacks have caused shipping companies to divert around South Africa's Cape of Good Hope. Electric car manufacturer Tesla said it was suspending most production at its German factory because of a parts shortage due to shipping delays linked to Huthi attacks.

© Agence France-Presse