Thirty-one U.S. special forces members in Afghanistan died aboard a NATO helicopter that crashed Saturday in an area reported to have insurgent activity, officials said. The crash occurred in the eastern province of Wardak, Afghan President Hamid Karzai's office said in a statement. It is among the worst single-day losses of American lives in the Afghan war. Seven Afghans were also killed during the crash in the restive central-eastern region, the statement said. A Taliban spokesman says the group claimed responsibility for shooting down the vehicle. NATO's International Security Assistance Force spokesman Justin Brockhoff confirmed the crash and acknowledged the helicopter had been flying in area where there was reported insurgent activity, but declined to offer additional details.