The US military early on Saturday struck another Houthi-controlled site in Yemen that they determined was putting commercial vessels in the Red Sea at risk.

That is according to two US officials who spoke anonymously to The Associated Press to discuss an operation that had not yet been publicly announced.

The first day of strikes on Friday hit 28 locations and struck more than 60 targets.

However, the US determined the additional location, a radar site, still presented a threat to maritime traffic, one official said.

On Friday, the US Navy warned American-flagged vessels to steer clear of areas around Yemen in the Red Sea and the Gulf of Aden for the next 72 hours after the US and Britain launched multiple air strikes targeting Houthi rebels.

The warning in a notice to shippers came as Yemen’s Houthis vowed fierce retaliation for the US-led strikes, further raising the prospect of a wider conflict in a region already beset by Israel’s war in Gaza.

US military and White House officials said they expected the Houthis to try to strike back.

President Joe Biden warned on Friday that the group could face further strikes.

The US-led bombardment — launched in response to a recent campaign of drone and missile attacks on commercial ships in the Red Sea — killed at least five people and wounded six, the Houthis said.

The US said the strikes, in two waves, took aim at targets in 28 different locations across Houthi-controlled areas of Yemen.

Mr Biden told reporters in Pennsylvania: “We will make sure that we respond to the Houthis if they continue this outrageous behaviour along with our allies.”

Asked if he believes the Houthis are a terrorist group, Mr Biden responded: “I think they are.”

The president, in a later exchange with reporters, said whether the Houthis are redesignated as such was “irrelevant”.

Mr Biden also pushed back against some US politicians, both Democrats and Republicans, who said he should have sought congressional authorisation before carrying out the strikes.

“They’re wrong, and I sent up this morning when the strikes occurred exactly what happened,” he said.

The White House said in November that it was considering redesignating the Houthis as a terrorist organisation after they began their targeting of civilian vessels.

The administration formally delisted the Houthis as a “foreign terrorist organisation” and “specially designated global terrorists” in 2021, undoing a move by former president Donald Trump.