The operation was conducted on Sunday night in Musa Qala district of Helmand which is under control of Taliban militants.
There were conflicting reports on the number of people killed and wounded in the operation and about their identities.
The Afghan Ministry of Defense said in a statement that 22 foreign militants were killed and 14 militants including five Pakistani nationals and a national of Bangladesh were arrested during an operation conducted in the area against the Taliban insurgents.
A huge ammunition cache of the group were also destroyed during the operation, the statement added.
The defense ministry further said that it will investigate claims of civilian casualties and will share the result with the people.
However, two officials from Helmand provincial council said the attack has targeted a wedding party and has left casualties to civilians including women and children.
“As a result of the operation 10 wounded people were taken to the emergency hospital and nearly 40 people including women and children are dead,” said Abdul Majid Akhundzada, a member of Helmand provincial council.
Meanwhile, provincial governor spokesman Omar Zwak said that 14 Taliban militants including foreign al-Qaeda members were killed in the operation conducted by Special Forces.
Helmand is among the volatile provinces in south of Afghanistan where the Taliban insurgent groups are actively operating in a number of its districts including Musa Qala.