US forces carried out fresh strikes on Yemen on Tuesday, an American official said, as the Iran-backed Houthi rebels claimed a missile attack on a Greek-owned cargo ship in the Red Sea. A string of Houthi attacks and retaliatory US and British strikes have heightened fears of Israel’s war on Gaza flaring across the region and disrupted trade in one of the world’s key maritime commercial routes. “The US conducted self-defence strikes against four Houthi ballistic missiles that posed an imminent threat to merchant vessels and US Navy ships,” a US official said on condition of anonymity, marking …