KANDAHAR, Afghanistan (AP) -- A car bomb exploded just outside the police headquarters of a southern Afghanistan city on Sunday, killing at least seven people, officials said.
The blast went off at a parking lot outside the police building in Kandahar, said Saisal Ahmad, a spokesman for the provincial government. Five police officers and two civilians were killed, and least 19 people were wounded, he added.
The blast was large enough that it shattered windows in nearby buildings.
No one immediately claimed responsibility.
Although the international military coalition in Afghanistan has poured resources into Kandahar city and surrounding areas in recent years as part of a push to take back insurgent strongholds, the area has remained dangerous and there have been repeated attacks against government installations.
In the north, meanwhile, Afghan police said that an American soldier shot and killed an Afghan guard at a U.S. base, apparently because the American thought the guard was about to attack him.
There have been a growing number of attacks by Afghan soldiers against international forces in Afghanistan in recent years, some the result of arguments and others by insurgent infiltrators. Last month, an Afghan soldier shot and killed four unarmed French troops last month at a base in eastern Afghanistan.
Friday's shooting in Sari Pul province in northern Afghanistan resulted from an unfortunate misunderstanding, said Sayed Jahangir, the deputy police chief for the province.
Afghans guard the outside perimeter of the base and Americans guard inside. Jahangir said that the Afghan guard -- a man named Abdul Rahim -- wanted to go into the base and started arguing with the American at the door. Rahim did not raise his weapon, but the American thought he was about to do so and fired, Jahangir said.
"Our initial reports show that the American thought he was acting in self defense," Jahangir said. Rahim was a private guard, not an Afghan soldier or policeman, Jahangir said.
U.S. forces were "aware of an incident in northern Afghanistan" and were investigating, said U.S. military spokesman Lt. Col. Jimmie Cummings. He declined to provide further details.