U.S. and British warplanes, ships and a submarine launched strikes across Yemen 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.

U.S. Lieutenant General Douglas Sims, the director of the Joint Staff, told reporters that 28 locations had been hit, using more than 150 munitions.

"I know we have degraded (their) capability," Sims said. "I don't believe that they would be able to execute the same way they did the other day. But we will see," he added.

Sims was referring to a attack on Tuesday by the Iran-backed group that led U.S. and British naval forces to shoot down 21 missiles and drones fired from Yemen. It was the largest attack in the area by the group to date.

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

Sims said Washington expected the Houthis to attempt to retaliate, adding the group had fired an anti-ship ballistic missile earlier in the day into the Red Sea. The missile did not hit any ships, he said.

The UK Maritime Trade Operations information hub said it had received reports of a missile landing in the sea around 500 metres (1,600 feet) from a ship about 90 nautical miles southeast of the Yemeni port of Aden.

While an assessment was ongoing on the damage from the strikes, Sims said he did not expect a large number of casualties since targets included rural areas.

(Reporting by Phil Stewart and Idrees Ali, Editing by Rosalba O'Brien)

By Idrees Ali and Phil Stewart