The Houthis are vowing to retaliate against US strikes in Yemen as the conflict escalates

Yemen's Houthi forces vowed on Friday to retaliate against US-led military strikes as the Middle East braced for a further escalation that could widen the conflict and further disrupt vital sea routes between Europe and Asia.

A pre-dawn strike on Friday with missiles and warplanes started by USA and UKwas in response to increased attacks on commercial vessels and warships in the Red Sea by Iran-backed Houthi militias, who said they were acting in solidarity with Palestinians in the war between Israel and Hamas.

Houthi military spokesman Yahya Sari said in a social media post that the US-led strikes “will not go unanswered and unpunished.” He said they killed at least five members of the Houthi forces, an armed group that controls northern Yemen, including the capital Sanaa.

US and British forces have fired more than 150 missiles and bombs at dozens of targets in Yemen, chosen specifically to damage the Houthis' ability to threaten shipping – weapons storage areas, radars and missile and drone launch sites – US officials said. It was the first Western strike after repeated warnings from the United States and its allies that the Houthis and Iran must stop their attacks at sea or face the consequences, only to see them grow.

“I expect they will try to retaliate in some way,” Lt. Gen. Douglas Sims, director of the US Joint Chiefs of Staff, told reporters on a conference call Friday, adding that it would be a mistake. “We're just not going to mess around here.”

John Kirby, the White House press secretary, said on Friday that the attacks ordered by President Biden were not intended to ignite a wider regional war.

“We are not interested in a war with Yemen — we are not interested in any conflict,” he said. “Virtually everything the president did was try to prevent any escalation of the conflict, including the strikes last night.”

Mr Kirby said everything the United States hit was a “genuine, legitimate military target”.

The British Prime Minister's office said that further strikes on Houthi targets are not planned at the moment, but the situation will be monitored.

On Friday, military analysts were still assessing the results of the strike, but General Sims said the strikes had achieved their goal of damaging the Houthis' ability to launch such a complex of unmanned and missile strikes they spent on Tuesday.

US and British forces struck more than 60 targets in 16 locations with more than 100 precision-guided munitions in the first wave of strikes, General Sims and other officials said. About 30 to 60 minutes later, the second wave hit dozens more targets in 12 additional locations with more than 50 weapons, they said.

Casualties were likely minimal because of the hour and the remoteness of many of the targets, General Sims said. He dodged questions about whether the Houthis were able to move men and equipment out of harm's way in advance amid widespread news reports that the strikes were imminent.

The ramifications of the Red Sea tensions have reached far beyond the Middle East. A number of commercial vessels bound for the Suez Canal were diverted following the American-led strikes. The International Association of Independent Tanker Owners, a trade association, said the US-led coalition had advised shipping companies to avoid the Bab el Mendab, a narrow strait at the mouth of the Red Sea, for “several days”.

The Suez Canal, which handles more than 20,000 ships a year and provides billions of dollars in transit fees for Egypt, saw traffic reduced as hundreds of ships diverted from the canal and the Red Sea, taking a much longer route around the southern tip of Africa, adding one to three weeks.

Mr Biden, confirming the attacks on Thursday night – early Friday morning in Yemen – said 2,000 ships had been forced to withdraw since mid-November.

In the three months since the Houthis began attacking commercial ships, the price of shipping a standard 40-foot container between China and northern Europe has more than doubled to $4,000 from $1,500, according to the Kiel Institute for World Economics, a German think tank.

The president called the strikes “a clear message that the United States and our partners will not tolerate attacks on our personnel or allow hostile actors to jeopardize freedom of navigation on one of the world's most important commercial routes.”

British warplanes took part in the strikes, while Australia, Bahrain, Canada and the Netherlands provided logistical, intelligence and other support, according to US officials.

The attacks sparked mass protests in Houthi-controlled areas of Yemen, and even some US allies in the Arab world said they worried the attacks would not deter the Houthis and could further inflame a region simmering over Israel's war against Hamas in the Gaza Strip.

Oman, a US ally that has brokered talks with the Houthis, criticized the strikes and expressed “deep concern”.

Saudi Arabia, wary of the breakdown of a fragile ceasefire in Yemen between the Houthis and the internationally recognized Saudi-backed government, said it was monitoring the situation in the Red Sea with “extreme concern”. After spending years and billions of dollars on the civil war in Yemen, the Saudis tried to get out of the conflict.

“The Kingdom reaffirms the importance of protecting security and stability in the Red Sea region,” the Saudi government said in a statement, adding a call for “self-restraint and avoidance of escalation.”

Russia requested an emergency meeting of the United Nations Security Council on Friday to discuss the US-led strikes, according to a diplomat from France, which holds the council's presidency this month. According to the diplomat, the meeting is scheduled for Friday afternoon and will have a closed consultative nature. On Wednesday, the Council passed a resolution condemning the Houthi attacks in the Red Sea, but did not authorize any retaliatory action.

Analysts studying the Houthis said on Friday that the US-led airstrikes could play into the group's agenda and were unlikely to stop the group's attacks.

“This was not a miscalculation by the Houthis,” said Hannah Porter, a senior researcher at ARK Group, a British international development company. “That was the goal. They hope to see an expanded regional war, and they really want to be on the front lines of that war.”

Hours after the strike, a senior Houthi official said the United States and Britain would soon realize they had committed “the biggest stupidity in their history.”

“Yemen is a difficult military adversary that can be quickly subdued,” official Mohammed al-Buhaiti said on social media. “He is ready to engage in a long-term battle that will change the direction of the region and the world.”

The war in Gaza has catapulted the Houthis, whose ideology has long included hostility to the United States and Israel, to unlikely prominence. Part of the group's slogan is “Death to America, death to Israel, curse the Jews.” Their raids in the Red Sea and their support for the Palestinian cause made them popular in the Arab world.

The group, which espouses a religious ideology inspired by a sect of Shiite Islam, has honed its military capabilities over the years of civil war. In 2014, it seized Sana'a and repelled a Saudi-led coalition that sought to oust it, deepening one of the world's worst humanitarian crises, leaving the Houthis in power in northern Yemen. There they created an impoverished proto-state, which they rule with an iron fist.

“They figured there weren't many high-value targets in the U.S. and U.K. because the country was already in ruins,” said Abdullah Baabud, an Omani senior fellow at Carnegie Middle East. “Therefore, they will not hesitate to continue testing the situation and escalating the conflict.”

Ms Porter agreed that the strikes were “highly unlikely” to stop the group's attacks in the Red Sea. “The Houthis are very comfortable working in wartime conditions,” she said. “They are more successful as a military group than as a government.”

The strikes could also help the Houthis domestically, said Ibrahim Jalal, a Yemen scholar at the Middle East Institute, a Washington-based think tank. A direct confrontation with the West provides “another excuse for a 'foreign enemy' to distract the public from their failed, underperforming rebel rule,” he said.

Hundreds of thousands of people in Yemen have died from fighting, starvation and disease since a Saudi-led coalition began bombing in 2015, backed by US weapons and military aid.

Aid groups and Yemeni analysts have warned that the new strikes, combined with an escalation in the Red Sea, could worsen Yemen's economic crisis by driving up the cost of fuel and food and deepening hunger.

“Yemeni people across the country have woken up to the fear of a return to conflict,” said Jared Rowell, head of the International Rescue Committee for Yemen. “Nine years of war have taken a huge toll, leaving more than 18 million people — more than half the population — in urgent need of aid.”

The report is prepared Eric Schmidt, Raja Abdulrahim, Zack Montague, Said Al-Batati, Stanley Reed, Farnaz Fasihi, Stephen's Castle and Gaya Gupta.