Those killed were members of Al Badar, the armed Afghan group of veteran leader Gulbuddin Hekmatyar, according to an unnamed Pakistani official.

Heykmatyar is an Afghan leader who fought against Soviet occupation in the 1980s and against the Taliban in the 1990s. He reportedly allied with the deposed group after the US-led invasion of Afghanistan in 2001, demanding the withdrawal of foreign forces.

US tensions

Friday's missile attack brings to five the number of such raids in the past two weeks.

Thirty-eight people, including women and children, have been killed in the past week's missile attacks.

Both the US military and the CIA operate drone aircraft armed with missiles of the type believed to have killed two senior al-Qaeda commanders in Pakistani territory earlier this year. Pakistan says it does not have missile-equipped drones.

Tensions between the US and Pakistan have further risen after a raid last week in which helicopter-borne US commandos landed in Pakistan's South Waziristan - the first known incursion into Pakistan by US troops since the 2001 invasion of Afghanistan.

Ashfaq Kayani, Pakistan's military chief, on Wednesday denounced the apparent US raids, saying unilateral actions risked undermining their co-operation.

He warned that "the sovereignty and territorial integrity of the country will be defended at all cost. No external force is allowed to conduct operations inside Pakistan."

A day later, The New York Times reported that George Bush, the US president, had secretly approved orders in July to allow US special forces to carry out ground assaults inside Pakistan without the approval of the Pakistani government.

Bajaur fighting

Concurrent with the attack in North Waziristan, Major Murad Khan, a Pakistani military spokesman, announced 32 fighters had been killed, as well as two soldiers, over the last day during violence in the Bajur region.

Pakistani officials say hundreds of fighters have been killed there during a week-long offensive, which has forced 500,000 people to flee their homes. Officials acknowledge that civilian have been killed and villages badly damaged in the fighting.

Rehman Malik, the Pakistani interior minister, had previously announced a government ceasefire with fighters in Bajaur and other tribal areas in honour of Ramadan, the Muslim month of fasting.