Sanaa - US and British forces struck Yemen early on Friday after weeks of disruptive attacks on Red Sea shipping.
The pre-dawn air strikes add to escalating fears of wider conflict in the region, which the United States, Britain and eight other allies said aimed to "de-escalate tensions".
China said it was "concerned about the escalation of tensions in the Red Sea", and news of the strikes sent oil prices up more than two percent.
US President Joe Biden called the strikes a "defensive action" after the Red Sea attacks and said he "will not hesitate" to order further military action if needed.
With fighter jets and Tomahawk missiles, 60 targets were hit by more than 100 precision-guided munitions, US Central Command said in a statement.
Unverified images on social media, some of them purportedly of Al-Dailami airbase north of the rebel-held capital Sanaa, showed explosions lighting up the sky as loud bangs and the roar of planes sounded. Huthi military spokesman Yahya Saree said at least five people had been killed.
Saudi call for 'restraint'
"The Kingdom of Saudi Arabia is following with great concern the military operations," a foreign ministry statement said after the US and British strikes. Riyadh called for "self-restraint and avoiding escalation".
Israel has also stepped up strikes against targets in Syria, and has exchanged regular fire with Lebanon's Hezbollah over its northern border.
Washington, which has said it seeks to avoid a spreading conflict, in December announced a maritime security initiative, Operation Prosperity Guardian, to protect shipping in the Red Sea route which normally carries about 12 percent of global maritime trade.
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