The US has hit radar sites in Yemen after one of its warships in the Red Sea came under missile attack for the second time in days.

The Pentagon said the sites were on territory controlled by Houthi rebels.

It marks the first time the US has fired at rebel targets since the start of the Yemen conflict in March 2015.

The US said initial assessments showed that three radar sites involved in the recent missile launches had been destroyed.

It 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."