WASHINGTON • An American warship has struck areas controlled by Yemeni rebels, launching three cruise missiles at radar installations that the Pentagon said had been used by the insurgents hours earlier to target another American ship.

The strikes were the first time the United States directly attacked Yemen's Houthi rebels, members of an indigenous Shi'ite group who are fighting the Yemeni government. The strikes were approved by President Barack Obama, the Pentagon said, warning of more to come if US ships were fired upon again.

"These limited self-defence strikes were conducted to protect our personnel, our ships and our freedom of navigation in this important maritime passageway," the Pentagon said in a statement. "The US will respond to any further threat to our ships and commercial traffic."

A senior US military official, who spoke on condition of anonymity, said the attack early yesterday was carried out by the USS Nitze, which fired Tomahawk cruise missiles.

Until yesterday, the Obama administration had tried to navigate a treacherous course in Yemen, publicly pushing for a peace deal while quietly providing military support to a Saudi Arabia-led coalition, which has been conducting a bombing campaign against the rebels since last year. Throughout, though, the administration has sought to keep the US from being dragged too deeply into the conflict.

That changed in the past four days with two separate missile attacks on an American destroyer, the USS Mason, that was sailing off the coast of Yemen. In both the first attack on Sunday and the second one on Wednesday evening, missiles were fired from areas under Houthi control, and though the missiles fell well short of the ship, American commanders believed the threat they posed was real.

The Mason was sailing in Bab el Mandeb, a strait at the southern end of the Red Sea, when it was fired upon on Wednesday. A second US ship nearby, the USS Ponce, was also untouched in the attack.

A Defence Department spokesman said the Mason was "conducting routine operations" when it was fired upon, and that it would continue to sail in the strait.

The Pentagon said the retaliatory strikes yesterday targeted three radar installations "involved in the recent missile launches threatening USS Mason and other vessels operating in international waters in the Red Sea" and the Bab el Mandeb strait.

"Initial assessments show the sites were destroyed," it added.

A US official said: "These radars were active during previous attacks and attempted attacks on ships in the Red Sea."

The official identified the areas as near Ras Isa, north of Mukha and near Khoka, adding that the sites were in remote areas where the risk of civilian casualties was low.

Yemen's Houthi movement yesterday reiterated its denial that it had carried out the failed missile attacks on the Mason, a news agency controlled by the group reported.

The Iranian-allied movement said the attacks did not come from areas under its control, reported Saba news agency, citing what it called a military source.

"These allegations are unfounded and the people's committees have nothing to do with this action," the agency, referring to the Houthi administration, reported the source as saying.

NYTIMES, REUTERS