Major-General Waheed Arshad said that the pre-dawn attack continued for several hours on Sunday, near Mir Ali, a town in the North Waziristan tribal region.

Arshad said: "The death toll is 15. They are all militants, the majority of them foreigners. They are mostly Uzbeks."

He had confirmed earlier reports that two women had been killed in the operation targetting two suspected militant compounds in the North Waziristan region, saying that they were "members of militant families".

According to a local administration official, four helicopters had took part in the operation.

The helicopters targeted at least six separate locations near military checkposts located between Mir-Ali and the region's main town of Miranshah.

Further violence 

The posts have come under repeated attack since pro-Taliban fighters scrapped a peace accord with the government in mid-July.

Sunday's attack came after a separate gun and bomb blasts in the area which had killed four Pakistani soldiers on Saturday.

Violence has intensified since July, following the breakdown of a 10-month peace deal with fighters in North Waziristan and the storming by the Pakistan army of the Red Mosque in Islamabad.

Ten soldiers and 17 fighters have been killed in bomb blasts and clashes in the Waziristan region since Thursday.

More than 200 people, most of them soldiers and policemen, have been killed in Pakistan's northwest since last month.