Kabul: A suicide car bomber struck a border police convoy on Monday in the Taliban's southern stronghold, killing at least two officers and a civilian in the second recent assault on forces led by a powerful police chief.

A Nato airstrike in central Afghanistan, meanwhile, killed three Afghan police officers mistaken for insurgents, the coalition said, in an operation liable to cause new friction between the international force and a government struggling to stabilise this war-ravaged nation.

The Taliban claimed responsibility for the suicide car bombing in Kandahar, the province that was the Taliban's birthplace. Qari Yousuf Ahmadi, a spokesman for the Taliban insurgency in the area, said fighters targeted the convoy and killed nine border police. Their claims are often exaggerated.

Bathhouse bombing

Zalmai Ayubi, spokesman for the Kandahar provincial governor, said the attack targeted forces led by Abdul Razaq, an influential border police head. Razak's deputy had been the apparent target of the bombing in a bathhouse in the same town, Spin Boldak, days earlier.

"They attacked my deputy, and now they are attacking my people," Razaq said, adding that a Pakistani ID card belonging to the latest bomber was found at the scene. "But I will root them out of my area."

Razak said the bomber killed three border police officers while Ayubi, the governor's spokesman, said two officers were killed, as was a civilian.

"They are trying to make me afraid but I will not stop," Razak said.

The bombings set back Nato claims to be making progress in battling the Taliban in the south, with stepped-up operations in the restive region. But as Nato presses the insurgents in the south, the Taliban has expanded the scope of their operations across the country, including areas once considered fairly quiet.

Nato said it was investigating the deaths of three Afghan police and the wounding of three others in central Daybkundi province in an apparent case of friendly fire.

The coalition said a team on the ground called in air support after seeing "nine armed individuals setting up what appeared to be an ambush position." The men later turned out to be Afghan police. "While we take extraordinary precaution while conducting operations to avoid friendly casualties, it appears innocent people may have been mistakenly targeted," said US Army Colonel Rafael Torres, a senior coalition spokesman. "We send our sincere condolences to their families and friends."

The strike was apparently launched following a mistranslation by an interpreter with the coalition forces, said Amanullah Gharji, deputy governor of the province. The Afghan police killed in the air strike were apparently mistaken for the insurgents, he said.