US officials have said airstrikes launched against Yemen’s Iran-backed Houthis will continue indefinitely, after a first round on Saturday killed at least 31 people and injured up to 100 more.

The strikes, which aim to punish the Houthis for their attacks against Red Sea shipping, are Donald Trump’s first such use of US military might in the region since he took power in January.

Pete Hegseth, the US defence secretary, told Fox News: “The minute the Houthis say ‘we’ll stop shooting at your ships, we’ll stop shooting at your drones’, this campaign will end, but until then it will be unrelenting.

The Houthis, an armed movement who have taken control of most of Yemen over the past decade, say they have targeted international shipping in solidarity with Palestinians and Hamas, which is also backed by Iran.