The Interior Ministry says the civilians were killed in the Kajaki district of Helmand province late Sunday.
There were conflicting reports about the reasons behind the killings. Some Afghan officials said the Taliban attacked the party because insurgents disapprove of music and dancing. But Helmand's governor said the killings took place after a long-standing feud between two Taliban commanders turned violent. And the governor of nearby Musa Qala district said insurgents killed the civilians because they had links to the government.
Authorities say it is difficult to corroborate the reports, because the area is not controlled by the government.
Later on Sunday, officials say insurgents overran an Afghan military post in Helmand's Washir district, killing 10 Afghan troops and wounding four others. A local official said five other Afghan soldiers were either kidnapped or joined the attackers.
Meanwhile, in eastern Afghanistan, NATO officials say an Afghan soldier turned his weapon on two coalition service members. NATO says its troops returned fire, killing the soldier.
The attack in Laghman province is the latest in a string of insider attacks this year.
Monday's attack brings the number of foreign soldiers killed in such violence this month to 12.
Last week, the commander of U.S. and NATO troops in Afghanistan, General John Allen, said many of the attacks are due to personal grievances and arguments, with about 25 percent attributed to Taliban infiltration, impersonation or coercion. VoA.
Some Veterans of the Afghan War believe 90% of "green on blue" violence involves Taliban infiltrators.