The U.S. ambassador in Kabul has told staff there that four U.S. Marines were killed in an explosion at the city’s airport and three wounded, a U.S. official with knowledge of the briefing said. Two explosions ripped through crowds of Afghans trying to enter the airport on Thursday.

At least three U.S. troops were injured, a U.S. official said. Witnesses reported multiple fatalities among the Afghans, many of whom were trying to enter the airport because they had assisted U.S.-led coalition efforts and feared persecution by the Taliban.