Dozens of people have been reported killed after US President Donald Trump ordered “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.

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.