WASHINGTON/ADEN, Yemen (Reuters) – U.S. and British warplanes, ships and submarines launched dozens of air strikes across Yemen overnight in retaliation against Houthi forces for months of attacks on Red Sea shipping that the Iran-backed fighters cast as a response to the war in Gaza.

Witnesses confirmed explosions at military bases near airports in the capital Sanaa and Yemen’s third city Taiz, a naval base at Yemen’s main Red Sea port Hodeidah and military sites in the coastal Hajjah governorate.

“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,” U.S. President Joe Biden said.

White House spokesman John Kirby said the strikes had targeted the Houthis’ ability to store, launch and guide missiles or drones, and that their impact was being assessed.

The Houthis, who have controlled most of Yemen for nearly a decade, said five fighters had been killed in a total of 73 air strikes. They vowed to retaliate and continue their attacks on shipping, which they say are intended to support Palestinians against Israel.

Shortly after 1500 GMT, the UK Maritime Trade Operations information hub said it had received reports of a missile landing in the sea around 500 meters (1,600 feet) from a ship about 90 nautical miles southeast of the Yemeni port of Aden. Three small boats were also reported to have neared the vessel.

The shipping security firm Ambrey identified it as a Panama-flagged tanker.

In Yemen, crowds gathered in cities. Drone footage on the Houthis’ al-Masirah TV showed hundreds of thousands of people in Sanaa carrying Palestinian and Yemeni flags and chanting slogans denouncing Israel and the United States.

“Your strikes on Yemen are terrorism,” said Mohammed Ali al-Houthi, member of the Houthi Supreme Political Council. “The United States is the Devil.”

The U.S. military said 60 targets at 16 locations had been hit using more than 100 precision-guided munitions.

In a poor country only just emerging from nearly a decade of war that brought millions to the brink of famine, people fearing an extended new conflict queued at petrol stations.

“There is a lot of worry that the fuel shortages will repeat themselves and food supplies will be scarce,” said Ali Ahmad, 52. “We are rushing to fuel our car and we bought flour and rice in case of any emergency because we are expecting the Houthis to respond and an escalation to take place.”

In Hodeidah, a resident who gave only his first name, Mahmoud, said troops were spreading through the streets and military vehicles were leaving barracks with security escorts.

Oil Price Jumps

The price of oil rose sharply on concern that supplies could be disrupted, with Brent crude up more than $2.

Commercial ship tracking data showed at least nine oil tankers stopping or diverting from the Red Sea.

INTERTANKO, an oil tanker industry body, sent a note to members saying the U.S.-led Combined Maritime Forces had advised ships to “stay well away from Bab al-Mandab”, the mouth of the Red Sea where 15 percent of global seaborne trade passes, for several days.

The strikes follow months of raids by Houthi fighters, who have boarded ships they claimed were Israeli or heading for Israel.

The United States and some allies deployed a naval task force to the area in December, and recent days saw increasing escalation. U.S. helicopters sank three Houthi boats on New Year’s Eve, killing fighters attempting to board a ship. On Tuesday, the United States and Britain shot down 21 missiles and drones in what they called the biggest attack yet.

However, not all major U.S. allies chose to back the strikes.

The Netherlands, Australia, Canada and Bahrain provided logistical and intelligence support, while Germany, Denmark, New Zealand and South Korea signed a joint statement defending the attacks and warning of further action.

But Italy, Spain and France chose not to sign or participate, fearing a wider escalation.

Egypt, which controls the Suez Canal linking the Red Sea to the Mediterranean, expressed deep concern.

A senior U.S. official accused Iran of providing the Houthis with military capabilities and intelligence to carry out their attacks.

Iran, which supports both the Houthis and the Hamas militants who control Gaza, condemned the strikes.

Iran-backed groups have increased attacks on U.S. targets in several countries since Hamas militants attacked Israel on Oct. 7, killing 1,200 people and precipitating the war in Gaza, which has so far killed more than 23,000.

Within hours of the air strikes, the U.S. Treasury Department issued sanctions targeting four oil tankers and two firms whose shipments it said were helping to finance the Houthis and Iran’s Quds Force.

Fears of Escalation

Houthi attacks have forced commercial ships to take a longer, costlier route around Africa, creating fears of a new bout of inflation and supply chain disruption. Container shipping rates for key global routes have soared this week.

Carmakers Tesla and Volvo, owned by China’s Geely, said delays to parts shipments from Asia had forced them to suspend some production in Germany and Belgium respectively, the first big manufacturers to make such announcements.

Washington has had to weigh its determination to keep the shipping lane open, and protect a fragile global economic recovery, against the risk of spreading unrest in a region already on edge.

It is unclear whether the strikes will in fact deter further attacks on shipping, said Tobias Borck, a Middle East security expert at Britain’s Royal United Services Institute.

The Houthis wanted to portray themselves as champions of the Palestinian cause and foes of the West, but were mainly concerned about retaining power.

“Is this the hill they want to die on?” said Mr. Borck. “They were doing well, they have been able to survive the last eight years, have expanded their power, but now they are inviting air strikes from the world’s most powerful military.”

But Farea Al-Muslimi, a Yemen expert at Chatham House think tank, noted that years of air strikes by Saudi Arabia had previously caused huge suffering to Yemenis while doing little to deter Houthi attacks: “Clearly it didn’t work.”

Saudi Arabia, which has sought for nearly a decade to oust the Houthis in a war that is now in a delicate stage of peace negotiations, called for restraint.