IDREE ALI  U.S. special forces have rescued an American citizen who had been kidnapped by armed men in an operation in northern Niger that is believed to have killed several of his captors, U.S. officials said. Forces including Navy SEALs rescued 27-year-old Philip Walton, who had been abducted on Tuesday from his home in neighbouring southern Niger, two U.S. officials said on condition of anonymity, adding that no U.S. troops were hurt. A diplomat source in Niger said Walton is now at the U.S. ambassador's residence in Niamey. "Big win for our very elite U.S. Special Forces today," U.S. President…