The US military has attacked radar sites in Yemen after a US warship in the Red Sea came under missile attack for the second time in days.
The Pentagon said initial assessments showed that three radar sites involved in the recent missile launches had been destroyed early on Thursday.
It said the targeted sites were on territory controlled by Iranian-allied Houthi rebels.
The Pentagon said the strikes had been authorised by President Barack Obama.
The attack was carried out using Tomahawk cruise missiles fired from the destroyer USS Nitze, according to US officials.
"These limited self-defence strikes were conducted to protect our personnel, our ships, and our freedom of navigation in this important maritime passageway," Pentagon spokesman Peter Cook said.
"The United States will respond to any further threat to our ships and commercial traffic, as appropriate."
They came hours after at least one missile was fired at the USS Mason, a guided-missile destroyer, in the Red Sea off Yemen.
The Pentagon said the ship took defensive action and suffered no damage.
On Sunday, two missiles were fired at the USS Mason from the same rebel-held territory.
Both missiles hit the water before reaching the ship, the Pentagon said.
At the time, a Houthi spokesman told the Saba news agency that it had not targeted any warships.
A Saudi-led multinational coalition, supported by the US, is carrying out an air campaign against the Houthi movement.
However, US support for the coalition has come under strain following an air strike on a funeral hall in the capital Sanaa earlier this month that killed at least 140 people; according to BBC.