CAIRO — Yemen’s Iranian-backed Houthi rebels captured a strategic island at the southern entrance to the Red Sea, two officials said Friday, opening a new front in the Iran war and further threatening Saudi oil exports through one of the world’s key shipping lanes. The Houthis’ biggest territorial gains in years, along the Bab el-Mandeb Strait , could boost Iran’s strategy of driving up world oil and gas prices to pressure the United States. Saudi Arabia struck the airport in the nearby port city of Mokha that the Houthis seized Thursday, a Houthi broadcaster said. There were no reports of damage or deaths. The capture of Mayun , a tiny, barren volcanic island inside the strait also known as Perim, was confirmed by a senior military official with Yemen’s internationally recognized government and by a Houthi official. Both spoke on condition of anonymity because they were not authorized to talk to journalists. Saudi Arabia, the world's largest oil exporter, has increasingly relied on the Red Sea to get its crude to market as an alternative to the Strait of Hormuz, where Iran h