President Trump says he has ordered a “decisive” military action against Houthi rebels in Yemen, opening a new salvo against the Iran-backed group that has targeted shipping lanes in the Red Sea.

The death toll from US strikes on Yemen has risen to 53, including five children, the Houthi rebels' health ministry said. The US said it launched a "decisive and powerful" wave of air strikes on Houthi targets on Saturday, with President Donald Trump citing Houthi attacks on shipping in the Red Sea as the reason.

Yemen's Houthi movement said on Sunday it was ready to "meet escalation with escalation" after U.S. strikes targeting the Iran-aligned group over its threat to resume Red Sea shipping attacks triggered a diplomatic backlash from Moscow and Tehran.