Dawood, the milita commander, said on Monday that the ambush took place late on Sunday in the troubled province of Helmand, where 3300 British troops will soon be based as part of a Nato plan to expand its Afghanistan peacekeeping force.
Mullah Mujahid, a Taliban commander, said in a telephone call that his men had killed five of the militiamen and captured six.
He said one Taliban fighter had also been killed in the fighting.
In some parts of Afghanistan, US forces hire local militiamen to help guard bases and convoys and to help on patrols.
Helmand has been plagued by insurgency since the Taliban were forced from power by the US and Afghan opposition troops in late 2001.

About 200 Taliban launched a series of attacks on government forces in Helmand on 3 February, when more than 20 people were killed in the biggest battle in the country in months.