Pakistani troops have continued a campaign against suspected rebel hideouts in a lawless tribal district for a third day as the death toll continued to rise, with local residents saying civilians have been killed in the operation.

Clashes between security forces and armed fighters were ongoing on Friday in the North Waziristan district, on the Afghan border.

The fighting started on Wednesday evening and was sparked by a suicide bombing that killed five soldiers at a checkpoint in the town of Mir Ali.

Rebels attacked the security forces as they returned from rescuing soldiers wounded in the bombing, prompting the military to respond with mortars, artillery and helicopter gunships in a large-scale search operation.

The death toll from the clashes rose to at least 40 on Friday as four more bodies were recovered from the debris of two hotels that came under heavy fire after fleeing fighters used them to take refuge.

The military says all of those killed in the operation were Taliban fighters, but locals said many of those who died in the hotels were drivers forced to stay there by a curfew imposed on Tuesday.

Nazir Khan Wazir, the member of parliament for the area, said most of those killed and wounded were not involved in the fighting.

"Most of those killed and wounded were innocent civilians. People are facing a terrible time. They are trapped in their houses," Wazir told the AFP news agency.

"Dozens of houses have been damaged by shelling. Residents are also facing food shortages."

Wazir appealed to the government to stop the bombardment to allow locals to bury their dead and take the wounded to hospital.

Taliban hub

The number and identity of those killed could not be verified independently because of the ongoing search operation and curfew.

The area is also off-limits to foreign journalists and aid groups.

North Waziristan is a major hub for Taliban and al-Qaeda linked groups in northwest Pakistan's seven semi-autonomous tribal districts.

The region is the focus of the US campaign of drone strikes targeting rebels, but sustained fighting of the sort seen in recent days is unusual.

The Tehreek-e-Taliban Pakistan group has led a bloody campaign against the Pakistani state in recent years, carrying out hundreds of attacks on security forces and government targets, mainly in the northwest.

Source: Agencies