Yemen's Iran-backed Huthis on Friday threatened to escalate attacks on Red Sea shipping after overnight strikes by the United States and Britain that the rebels said killed 16 people.

The toll announced by the Huthis, which AFP could not independently verify, would be one of the deadliest strikes since the US and Britain started their campaign in January against disruption of the vital trade route.

The rebels, who control much of Yemen, have carried out scores of drone and missile attacks on vessels in the Red Sea and Gulf of Aden since November, citing solidarity with Palestinians in the Gaza Strip over the Israel-Hamas war.

The US Central Command, CENTCOM, said 13 Huthi sites were targeted in the latest strikes.

"The American-British aggression will not prevent us from continuing our military operations," Huthi official Mohammed al-Bukhaiti said on X, formerly Twitter, vowing to "meet escalation with escalation".

AFP journalists heard explosions in the capital Sanaa and the port city of Hodeida overnight from Thursday to Friday.

Strikes also targeted telecoms infrastructure in the city of Taez, the rebels said.

In a statement on X, Huthi military spokesperson Yahya Saree said 16 people were killed and more than 40 were wounded in Hodeida alone, including an unspecified number of civilians.

In response, the rebels launched a missile attack on US aircraft carrier the USS Dwight D. Eisenhower in the Red Sea, Saree said, an operation that Washington has yet to confirm.

The Huthis "will not hesitate to respond directly and immediately to every new aggression on Yemeni territories", Saree said.

- 'Ongoing threat' -

Yemen's Huthi-controlled Al-Masirah TV broadcast a video showing bloodied men wounded in a purported strike on a building housing a radio station in Hodeida.

The channel showed victims receiving treatment at a hospital, although AFP could not independently verify the authenticity of the images.

A hospital employee in Hodeida said many militants were among those killed and wounded in the attack, but was unable to give exact figures.

The British defence ministry said its warplanes launched strikes in "a joint operation with US forces against Huthi military facilities".

The ministry said intelligence indicated two sites near Hodeida were involved in the attacks on shipping, "with a number of buildings identified as housing drone ground control facilities and providing storage for very long-range drones, as well as surface to air weapons".

Another "command and control" site had been identified further south, it said in a statement.

British Prime Minister Rishi Sunak said "the strikes were taken in self-defence against an ongoing threat", adding the rebels had carried out 197 attacks since November.

CENTCOM said the strikes were "necessary to protect our forces, ensure freedom of navigation, and make international waters safer and more secure".

Iran condemned the US-UK military action, saying it aims to "spread insecurity in the region".

The "governments of the United States and the United Kingdom are responsible for the consequences of these crimes against the Yemeni people", said its foreign ministry spokesman, Nasser Kanani.

- Drone claim -

Since January, the United States and Britain have launched repeated strikes on Huthi targets in Yemen in response to the rebels' harassment of shipping.

In February, the Huthis held a mass funeral in Sanaa for 17 fighters they said were killed in US and British strikes.

The US-UK reprisals have not stamped out the campaign by the rebels, who have vowed to target US and British vessels as well as all ships heading to Israeli ports.

On Wednesday, the rebels said they had attacked a Greek-owned bulk carrier and several other vessels in response to Israeli strikes on Rafah in the Gaza Strip.

The Huthis also said they shot down a US MQ-9 Reaper drone with a surface-to-air missile, claiming it was the sixth such aircraft they have downed in recent months.

Among the biggest Huthi attacks, in March a ship loaded with fertiliser sank in the Gulf of Aden after it was damaged by Huthi missiles.

And in November, the rebels seized the vehicle transporter Galaxy Leader and its crew after boarding it via helicopter.

The Huthi attacks have prompted some shipping companies to detour around southern Africa to avoid the Red Sea route, which normally carries about 12 percent of global trade.