The militants were killed during three days of clashes in southern Uruzgan province, said provincial police chief Juma Gul Himat on Wednesday. Nine other militants and five policemen were wounded.
Authorities detained 10 other militants following the operation near the provincial capital of Tirin Kot, Himat said. The report could not be independently verified because of the remoteness of the area.
Afghanistan is facing a raging insurgency nearly seven years after the Taliban were ousted from power, and the country's south is the primary hub for the militancy.
More than 2,700 people - mostly militants - have died in insurgency-related violence this year, according to an Associated Press tally of figures provided by Afghan and Western officials. Insurgent attacks are reported to have risen by 50 percent so far this year compared to 2007.
Separately, a NATO soldier died after insurgents attacked his convoy in southern Helmand province on Tuesday, the military alliance said.
Later Wednesday, Britain's Ministry of Defense said one of its soldiers had died in Helmand, the 114th British serviceman to be killed in Afghanistan since operations began there in November 2001.
It was unclear whether NATO and the British Defense Ministry were referring to the same soldier.