Insurgents beheaded 17 civilians in a Taliban-controlled area of southern Afghanistan, apparently because they attended a dance party that flouted the extreme brand of Islam embraced by the militants, officials said Monday.The killings, in a district where U.S. Marines have battled the Taliban for years, were a reminder of how much power the insurgent group still wields in the south — particularly as international forces draw down and hand areas over to Afghan forces.The victims were part of a large group that had gathered late Sunday in Helmand province's Musa Qala district for a celebration involving music and dancing, said district government chief Neyamatullah Khan. He said the Taliban slaughtered them to show their disapproval of the event.All of the bodies were decapitated but it was not clear if they had been shot first, said provincial government spokesman Daoud Ahmadi.Information was only trickling out slowly because the area where the killings occurred is largely Taliban controlled, Khan said. The Taliban spokesman for southern Afghanistan could not be reached for comment.Many Afghans and international observers have expressed worries that the Taliban's brutal interpretation of Islamic justice will return as international forces withdraw.Under the Taliban, who ruled the country from 1996 to 2001, all music and film was banned as un-Islamic, and women were barred from leaving their homes without a male family member as an escort.