German troops in northern Afghanistan have killed five Afghan soldiers, Nato has said.

The troops were in two civilian cars which did not heed warnings to stop as they drove up to German troops in Kunduz province, a Nato statement said.

The Nato forces are said to have been en route at the time to the scene of a clash with Taliban insurgents that left three German soldiers dead.

Germany has the third-largest foreign contingent in Afghanistan.

Nato's International Security Assistance Force (Isaf) said in a statement it regretted the loss of life in Friday evening's friendly fire incident.

The two unmarked civilian cars involved are thought to have been an Afghan National Army patrol en route to Kunduz city, Isaf said.

Map of Afghanistan

The statement said: "Although the [Isaf] force attempted to stop the cars using a variety of methods, both vehicles continued to approach.

"The force eventually fired on the vehicles, killing at least five Afghan soldiers."

Earlier on Friday, three German soldiers died and a number were seriously wounded in a battle with Taliban insurgents in the province.

German military participation in Afghanistan has been deeply unpopular with the German public.

The German parliament voted in February to increase the contingent by up to 850 troops to a total of 5,350.

Dozens of Afghan civilians died last September in Kunduz when German commanders called in a Nato air strike on two hijacked fuel trucks, sparking a political furore in Berlin which continues.