Airstrikes led by the United States and Britain overnight in Yemen left five Houthi fighters dead and six others injured, the Iran-aligned rebels said on Friday, vowing retaliation which also fuelled fears of a major regional escalation. “All American and British interests have become legitimate targets for the Yemeni Armed Forces in response to their direct and declared aggression on the republic of Yemen,” the rebels’ ruling Higher Political Council said, according to the Houthi-controled Saba news agency. “Americans and the Britons should not believe they will escape punishment of our valia…