KABUL - Suicide bombers struck inside Afghanistan's fiercely anti-Taliban Panjshir valley on Saturday, the first time in a decade of war that the insurgents have managed to use their trademark tactic in the normally peaceful northern province.

Four bombers targeted the Provincial Reconstruction Team headquarters, which houses US and Afghan troops and civilians, around dawn, Afghan and NATO officials said. ? ?

They were halted outside the base, but the deputy provincial Governor Abdul Rahman Kabiri said they had killed two civilians and wounded two guards when they detonated their explosives. ?

Panjshir Provincial Police Chief Qaseem Junglebagh disputed that toll and said the four men were all shot dead by security forces before they could set off the bombs. ?

A spokesman for NATO-led forces confirmed there had been a suicide attack, but said the compound was not breached and there were no foreign casualties.

The Taliban claimed responsibility for the attack, and said the bombers were from Panjshir province.

If true, it would be an alarming sign of growing Taliban support outside their traditional heartland, as the valley was one of the few places in Afghanistan never subdued by the group.

"This attack made a bad day for foreign invaders in the province for the first time," Taliban spokesman Zabihullah Mujahid said in a statement.

"There is no secure place for them in the country," he said.

The attack will raise fresh concerns about the readiness of Afghan police and soldiers to provide security after foreign combat troops head home, as it was one of the first parts of the country handed over to local forces. ?

Picturesque Panjshir, famous for its jagged cliffs and deep valleys, is now under Afghan security control, and strict checks take place on most vehicles and passengers entering the area.

The handover took place in July but foreign troops have remained in the province to carry out reconstruction work.