Washington: The United States and Britain struck Houthi rebels over the Iran-backed group's attacks on shipping in the Red Sea, US media reported on Thursday, as witnesses reported air strikes in Yemeni cities.

The strikes involved fighter jets and Tomahawk missiles, several US media said. In a statement, US President Joe Biden said the strikes on the Houthis were carried out with "support" from Australia, Bahrain, Canada and the Netherlands, adding that he "will not hesitate" to order further military action if needed.

"Today, at my direction, US military forces... successfully conducted strikes against a number of targets in Yemen used by Houthi rebels to endanger freedom of navigation in one of the world's most vital waterways," Biden said.

"These targeted strikes are a clear message that the United States and our partners will not tolerate attacks on our personnel or allow hostile actors to imperil freedom of navigation in one of the world's most critical commercial routes," he added.

Air strikes hit a number of cities in Yemen, where the Houthis control a swathe of territory, a Houthi source and witnesses said.

The Houthis have carried out a growing number of attacks on the key international sea route since the Gaza war erupted with Hamas's unprecedented attack on Israel on October 7. But the Western strikes risk turning an already tense situation in the Middle East into a wider conflagration pitting the United States and Israel against Iran and its regional proxies.

British Prime Minister Rishi Sunak also convened an emergency cabinet meeting in London on Thursday to discuss the strikes against the Houthis, UK media reported.

The Houthi rebels say they are acting in response to Israel's bombardment of the Gaza Strip, and have launched a series of drones and missiles towards Israel. They have controlled a major part of Yemen since a civil war erupted there in 2014, and are part of the Iran-backed so-called "axis of resistance" arrayed against Israel.

The United States and its allies had issued a series of increasingly stern warnings to the Houthis to stop the shipping attacks, although Washington has been cautious about the risks of further inflaming regional tensions.

Washington set up an international coalition in December -- dubbed Operation Prosperity Guardian -- to protect maritime traffic in the area, through which 12 per cent of world trade flows.

Consequences
Twelve nations led by the United States then warned the Houthis on January 3 of "consequences" unless they immediately stopped attacks on commercial vessels. But late Tuesday the Houthis launched what London called the most significant attack yet by the Yemeni rebels, with US and British forces shooting down 18 drones and three missiles.

British Defense Secretary Grant Shapps then said on Wednesday that "enough is enough" and told the Houthis to "watch this space." The UN Security Council also on Wednesday urged an immediate halt to the attacks on shipping, warning of a threat to regional peace and security. 

The final straw for the Western allies appeared to come early on Thursday when the US military said the Houthis 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 bypass the route and instead divert around South Africa's Cape of Good Hope, sparking fears of a shock to the global economy. 0The Houthis say they only target vessels linked to Israel or its allies.

The United States strengthened its military posture in the region immediately after the October 7 attacks on Israel and warned Iran and its allies not to escalate the situation.

The Biden administration was initially cautious in its response as it is seeking to preserve a fragile peace in Yemen, where a decade of civil war and a Saudi-led coalition's military campaign has caused one of the world's worst humanitarian crises in the Arabian peninsula's poorest country.

A truce between the Houthis and the Saudi-backed, internationally recognized government has largely been held since April 2022.