Dubai: The US military directly targeted Yemen's Huthi rebels for the first time on Thursday, hitting radar sites controlled by the insurgents after US warships came under missile attacks twice in four days.
The Iran-backed rebels have denied carrying out the attacks, which saw missiles fired at US warships in the Red Sea on Sunday and Wednesday but falling short of their targets.
The United States is providing logistical support to a Saudi-led coalition that has been battling the rebels since last year, but Thursday's strikes marked the first time Washington has taken direct action against the Huthis.
The Pentagon said the cruise missile strikes — authorised by President Barack Obama — were launched at 4.00 am local time (0100 GMT) by the destroyer USS Nitze against territory on Yemen's Red Sea coast controlled by the Huthis.
"Initial assessments show the sites were destroyed," Pentagon Press Secretary Peter Cook said in a statement.
The strikes "targeted radar sites involved in the recent missile launches threatening USS Mason and other vessels operating in international waters in the Red Sea and the Bab al-Mandeb (Strait)," it added.
"These limited self-defence strikes were conducted to protect our personnel, our ships, and our freedom of navigation in this important maritime passageway."
The USS Mason, a destroyer, was targeted on Wednesday by a missile fired from rebel-held territory which crashed into the ocean before reaching its target.
The Mason and the USS Ponce, an amphibious staging base, were previously targeted on Sunday by two missiles that also fell short.
"The United States will respond to any further threat to our ships and commercial traffic, as appropriate, and will continue to maintain our freedom of navigation in the Red Sea, the Bab al-Mandeb, and elsewhere around the world," Cook said.
A Yemeni military source said the US missiles hit radar sites near Al-Makha and Al-Khukha in southwestern Yemen and Ras Isa, further north along the coast.
Attack claims 'baseless': rebels
The Huthis said the accusations they had fired on US warships were "baseless".
"Such claims aim to create false justifications to step up attacks and to cover up for the continuous crimes committed by the aggression against the Yemeni people," the rebel-controlled Saba news agency quoted a military official allied with the rebels as saying on Thursday.
The Saudi-led coalition launched its campaign in March last year, after the rebels seized control of large parts of Yemen including the capital Sanaa, forcing the government of President Abedrabbo Mansour Hadi to flee.
The coalition has since carried out hundreds of air strikes and provided ground troops to support Hadi's forces, but it has failed to dislodge the rebels — who are allied with forces loyal to ex-president Ali Abdallah Saleh — from key areas.
The US military provides intelligence and refuelling for coalition aircraft. It also supplies advanced munitions and logistics support to the effort, and is Saudi Arabia's biggest arms supplier.
The campaign has faced increasing international criticism over civilians deaths, with critics calling on Washington to end its support for the coalition.
After a coalition air strike on a funeral in Sanaa on Saturday killed more than 140 people, the US administration announced an "immediate review" of its cooperation.
'Unlawful' funeral strike
Human Rights Watch, which has regularly criticised the Saudi intervention, on Thursday said the funeral strike needed to be investigated as "an apparent war crime".
"While military personnel and civilian officials involved in the war effort were attending the ceremony, the clear presence of several hundred civilians strongly suggests that the attack was unlawfully disproportionate," it said in a statement.
Francois Heisbourg, an analyst at the Paris-based Foundation for Strategic Research, said the rebels were probably looking to send a message to Washington after the funeral strike.
"The most logical explanation is that the Huthis... wanted to show the Americans that there is a price to pay" for continuing to support the Saudis, he said.
But Heisbourg said it was unlikely that Thursday's strikes were a sign of Washington stepping up its participation in the coalition.
"They reacted in a limited manner and it should stop there," he said.
Yemen's conflict has killed more than 6,800 people, wounded more than 35,000 and displaced at least three million since the coalition launched military operations, according to the United Nations.
As well as supporting the coalition, Washington has for years carried out drone attacks against jihadists in Yemen, regularly killing members of the local branch of Al-Qaeda.