Police officers die in Afghanistan blast

A large explosion has hit just outside the police headquarters in a southern Afghanistan city, killing at least five police officers and two civilians.

The blast went off in a car park outside the police building in Kandahar, said Saisal Ahmad, a spokesman for the provincial government.

Five officers and two civilians were killed and another 19 people were wounded, including 10 civilians, the provincial government said.

The blast was large enough that it shattered windows in nearby buildings.

No one immediately claimed responsibility.

In the north, meanwhile, Afghan police said that an American soldier shot and killed an Afghan guard at a US base, apparently because the American thought the guard was about to attack him.

There has 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 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 defence," Jahangir said. Rahim was a private guard, not an Afghan soldier or policeman, Jahangir added.

US forces were "aware of an incident in northern Afghanistan" and were investigating, said US military spokesman Lt Col Jimmie Cummings. He declined to provide further details.