Islamabad - Taliban militants clashed with Pakistani security forces Thursday as they moved into the north-western district of Buneer, said an official, as Western leaders worried over the mounting threat to the Pakistani government.

The movement of eight platoons of Frontier Constabulary seems to have failed in blocking Taliban who reportedly have invaded another neighbouring district of Shangla.

The insurgents fired at the two platoons of paramilitary troops from their positions in the mountains in the Chinglai area of Buneer district as they headed to guard the government buildings in the area.

"One policeman in a police squad escorting the paramilitary troops died and another was injured," said local police official Rasool Khan. "The troops retreated following the attack while the insurgents are still holding their positions on the hilltops."

Hundreds of Taliban infiltrated Buneer district from the militancy-plagued Swat valley days after President Asif Ali Zardari signed a peace deal with the Taliban to end a 16-month long conflict in the Swat valley.

As the clashes were taking place in Buneer, more than 30 Taliban fighters entered another district of Shangla, that borders both Swat and Buneer, Geo television reported citing eye-witnesses. However, the local officials in Shangla denied the report.

The Taliban expansion is perceived as a direct threat to Islamabad, located only 100 kilometres south-west of Buneer.

"I think that the Pakistani government is basically abdicating to the Taliban and to the extremists," US Foreign Secretary Hilary Clinton told the House Committee on Foreign Affairs on Wednesday.

"We cannot underscore the seriousness of the existential threat posed to the state of Pakistan by the continuing advances, now within hours, of Islamabad," she said.

According to her, the militants are "seeking the overthrow of the Pakistani state." (dpa)