The militants were killed in Nadi Ali district of Helmand on Wednesday after they ambushed a police vehicle in the province, a main Taliban bastion and the biggest drug-producing region of Afghanistan, world's top supplier of heroin.

"It is worth mentioning that Mullah Naqibullah who was regarded as a prominent commander of the Taliban is amongst those killed," the ministry said in a statement.

Naqibullah twice escaped from Afghan government prisons, the statement said. He boasted earlier this year he had managed to flee after paying a $15,000 (7,600 pound) bribe, local media said.

The Taliban could not be immediately contacted for comment.

The fighting is part of a rising tide of violence in Afghanistan where more than 11,000 people have been killed in the last two years, the bloodiest period since the Taliban's 2001 ouster.

The al Qaeda-backed Taliban are spearheading an insurgency against the pro-Western Afghan government and foreign troops led by NATO and the U.S. military.