"But, popularly, it is believed that this is the kind of attack the US has made within this very troubled area of Pakistan before, and they are also likely to be behind these attacks," he said.

In depth

Pakistan army 'taking back' Swat Valley

"Drone strikes are causing much controversy in Pakistan - many people say they have killed innocent civilians and act as a recruitment tool for the Pakistan Taliban."

Up to 11 people were also reported to have been killed in an attack by Pakistani aircraft on two targets in North Waziristan.

The attacks were the latest in more than 40 such raids by the US against targets in the border area since last August.

Narrow escape

The raids came as the Pakistani military prepares for an offensive in South Waziristan against Mehsud, who has been blamed for a string of deadly suicide attacks across the country that have killed more than 100 people in the past month.

The US has stepped up attacks on targets linked with Mehsud with missiles fired from unmanned drones.

The Taliban leader last week narrowly escaped a missile attack on a funeral for militants killed in an earlier drone attack.

Eighty people died in the strike, although Mehsud escaped unharmed.

In Pakistan's Swat valley, the Pakistani military said it had driven out most pro-Taliban fighters after nearly three months of fighting.

Bloodied cleavers

Al Jazeera's Kamal Hyder, who was given exclusive access to areas of Swat now controlled by the military, said: "The battle for Swat has been a battle for higher ground.

"The Pakistani military says it is confident that it will be able to root out the militancy problem in the valley.

"They have already regained the high ground overlooking the strategic valleys and now say their men are fighting last pockets of resistance."

He said he was shown former Taliban strongholds and captured weapons ranging from heavy machine guns and rocket-propelled grenades to large, bloodied knives  and cleavers believed to have been used to decapitate prisoners.

The Pakistani government signed a peace deal in February with Sufi Mohammad, a pro-Taliban leader in Swat, in a bid to end 18 months of fighting in the northwest of the country.

But the truce came to an end just two months later, when Taliban supporters moved into neighbouring Bunir district in April and the Pakistani military re-started its offensive.

Around 2.5 million residents of Swat have fled their homes to avoid the conflict, triggering a humanitarian crisis as relatives and government-run camps struggle to cope.