A suspected homicide bomber attacked a guard post outside the police headquarters in the main city in southern Afghanistan, killing 13 people and wounding 11, officials said.

Ten of the dead and five of the wounded were police who were standing guard when the assault occurred, said Mamoon Khan, a doctor at Kandahar city's Mirwaise Hospital, which was treating the injured. The rest of the victims were civilians.

Jan Mohammed, a senior police officer at the site of the blast in Kandahar, said the explosion occurred after the attacker drove a motorbike into the guard post.

The post is up against a concrete wall that surrounds the heavily guarded police headquarters. Several cars and motorbikes in the area were destroyed, but the wall and the buildings inside the police compound were not damaged.

A reporter for The Associated Press said he saw three bodies lying on the ground covered in blood and several wounded people being carried away.

Afghan and Canadian troops cordoned off the area.

The attack is the latest in a string of bombings in Kandahar, a former Taliban stronghold. The violence has raised fears for the country's nascent democracy four years after the Taliban were ousted for hosting Usama bin Laden.