The incident could further strain relations between the key US allies in the war on terrorism after a sharp deterioration in ties over Afghan accusations Taliban fighters were finding sanctuary in Pakistan.

General Abdul Raziq, an Afghan army officer in the border town of Spin Boldak, said on Wednesday his forces had killed 16 Taliban after surrounding them in mountains, 8 km east of the town, near the Pakistani border.

But many residents of Spin Boldak, in Afghanistan's southern Kandahar province, dismissed that explanation and organised a strike on Thursday to protest against the killings.

"We have sent a team to investigate the matter," Assadullah Khalid, the governor of Kandahar province, said on Thursday.

"If what residents say is true, then the culprits will be punished," he said.

Afghanistan has seen a surge in bomb and other attacks by Taliban insurgents and their militant allies in recent months. The Taliban have vowed to launch a spring offensive against foreign forces and the Western-backed government.

Pakistani Interior Minister Aftab Ahmed Khan Sherpao said those killed were Pakistanis visiting Afghanistan for a traditional new year holiday.

"They were all Pakistanis who had gone for Now Rouz," Sherpao told a Pakistani television channel, referring to the holiday.

He said one of those killed was wanted by Pakistani authorities but added: "They were not Taliban".

A Pakistani Foreign Ministry spokeswoman said the government had asked Afghanistan about the incident and had been told authorities were investigating.

General Raziq said that two Taliban commanders, Mullah Atta Jan and Shish Noorzai, known to have organised suicide attacks and ambushes, were among those killed by his troops.