A suspected suicide bomber drove a motorcycle into a guard post outside police headquarters in the southern Afghan city of Kandahar, killing 13 people and wounded 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.
A senior police officer at the site of the blast, Jan Mohammed, said the bomb destroyed a guard post outside the police headquarters.
The attacker drove a "motorbike straight into the guard post and then there was an enormous explosion," he said.
The site of the blast 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. Afghan and Canadian troops cordoned off the area.
The attack is the latest in a string of bombings in Kandahar, a former Taliban stronghold.