Northern Afghanistan used to be the safest region in the country until 2007 but has seen a surge in Taliban-led attacks.

Hundreds of Taliban militants returned to their former bases after they were driven from two districts in the province by Afghan and German forces.

The 10-day operation involving some 300 German troops and nearly 1,000 Afghan soldiers cleared Chardarah district, the main hotbed for Taliban in the province, and left some 17 insurgents dead.

But the militants came back to the district after the joint operation ended late last month, posing a serious threat to the Aug 20 presidential election.

Around 4,000 German troops are stationed in the northern region.