As witnesses in Yemen confirmed explosions throughout the country to Reuters, US President Joe Biden cautioned in a statement late on Thursday he would not hesitate to take further action if needed.
"These targeted strikes are a clear message that the United States and our partners will not tolerate attacks on our personnel or allow hostile actors to imperil freedom of navigation," Biden said on Thursday.
Rishi Sunak and Joe Biden have authorised joint attacks on Houthis in Yemen. (AP PHOTO)
Britain's ministry of defence said in a statement that "early indications are that the Houthis' ability to threaten merchant shipping has taken a blow".
Iran, which supports the Houthis, strongly condemned the attacks.
A spokesperson for the Houthis said there was no justification for the attacks and the group would continue targeting ships heading towards Israel.
Russia said it had requested an urgent meeting of the United Nations Security Council to discuss the military strikes.
The Houthis say their attacks on shipping routes in the Red Sea are a show of support for the Palestinians and Hamas, the Islamist group that controls Gaza.
US Defense Secretary Lloyd Austin, who is in hospital due to surgery complications, said in a statement that the strikes targeted Houthi capabilities including drones, ballistic and cruise missiles, costal radar and air surveillance.
A Houthi official confirmed "raids" in the capital Sanaa along with the cities of Saada and Dhamar as well as in Hodeidah governorate, calling them "American-Zionist-British aggression".
Witnesses told Reuters the raids targeted a military base adjacent to Sanaa airport, a military site near Taiz airport, a Houthi naval base in Hodeidah and military sites in Hajjah governorate.
The Houthis say their attacks in the Red Sea are a show of support for Palestinians and Hamas. (AP PHOTO)
The US said Australia, Bahrain, Canada and the Netherlands supported the operation and sought to present the strikes as part of an international effort to restore the free flow of trade in a key route between Europe and Asia that accounts for about 15 per cent of the world's shipping traffic.
But the strikes, the first on Yemeni territory since 2016, were also an undeniable demonstration of Washington's struggle to contain the fallout of the Israel-Hamas war in the Middle East since its eruption in October.
"The concern is that this could escalate," said Andreas Krieg at King's College in London, warning of the risk that Saudi Arabia and the United Arab Emirates could also be drawn into the confrontation.
In a statement after the strikes, Saudi Arabia called for restraint and "avoiding escalation".
The US also accused Iran of being involved operationally in the Houthi attacks in the Red Sea, providing the military capabilities and intelligence to carry them out.
The strikes were carried out by aircraft, ship and submarine.
"We were going after very specific capability in very specific locations with precision munitions," a US military official said.
The Houthis, who control most of Yemen, have defied UN and international calls to end their attacks. (EPA PHOTO)
The Houthis, who control most of Yemen, defied UN and international calls to halt their missile and drone attacks on Red Sea shipping routes and warnings from the US of consequences if they failed to do so.
The Houthi attacks have disrupted international commerce, forcing international shipping to take the long route around South Africa to avoid being struck.
The increase in delivery costs is stoking fears it could trigger a fresh bout of global inflation.
The strikes followed other diplomatic and military steps US officials had hoped would halt the Houthi attacks without starting a fresh conflict.
In December, more than 20 countries agreed to participate in a defensive US-led coalition, Operation Prosperity Guardian, to safeguard commercial traffic in the Red Sea.
The US and British strikes are taking place outside that coalition.
