A remote-controlled bomb hit a convoy of German peacekeepers in northern Afghanistan Wednesday, killing an Afghan driver and three civilians, officials said.

The attack came added to deteriorating security ahead of September elections, and just a week after 11 Chinese workers were shot in their beds in the same province.

Mutaleb Beg, the provincial police chief, said the roadside bomb exploded in Kunduz, 150 miles north of Kabul.

"The convoy was passing through the Gandum Bazaar market when a mine was detonated on the edge of the road by remote control," Beg told The Associated Press.

He said shrapnel cut through a sport utility vehicle belonging to the peacekeepers at the rear of the line of German military vehicles, killing the driver.

He said two children, about 10 years old, and an elderly man also died. A third child was injured.

In Germany, military spokesman Udo Groebner confirmed the four deaths. He said the 250-strong German contingent had loaned the vehicle to a relief agency, but didn't give details.

Kunduz is the only place outside the Afghan capital where the 6,400-strong NATO-led security force has a presence, though it plans to set up at least five more bases across the north in time for the elections.

Insurgents active mainly in the south and east of the country have vowed to sabotage the vote, and appear to be expanding into the relatively stable north.

The 11 Chinese workers and an Afghan guard were killed last Thursday in Kunduz province in the worst attack on foreign civilians since the fall of the Taliban regime in late 2001.

Five members of medical relief agency Medecins Sans Frontieres (search), including three Europeans, were fatally shot in the remote northwest on June 2. The organizations is known in English as Doctors Without Borders.

A second explosion early Wednesday damaged the office of Afghanaid (search), a British relief agency, in Faizabad in northeastern Badakhshan province, slightly injuring an Afghan guard.

Afghanaid director Dave Mather said he had no idea why it was targeted. "We've been here more than 10 years and are extremely well known. It's a bit of a mystery."

Meanwhile, the U.S. military reported a clash between American troops and militants in southeastern Khost province.

About 10 rockets were fired at the soldiers, causing no injuries or damage, spokesman Lt. Col. Tucker Mansager said.

More than 500 people have died in violence across the country this year, also including government officials, Afghan and foreign soldiers and scores of suspected militants.

The bloodshed is hampering U.N. efforts to register voters in the south and east, but both the U.S. military and President Hamid Karzai (search) say the vote should go ahead.