Pakistan says it has killed 60 militants in North Waziristan in the deadliest air strikes in months, throwing peace talks into doubt.
A military statement said the dead included "important commanders" and foreigners, but did not specify who.
Local residents in the Mir Ali area described hearing huge explosions after helicopters and jets flew overhead in the early hours.
North Waziristan is a stronghold of Taliban and al Qaeda-linked militants.
It is one of seven lawless tribal agencies, but the army have pushed the militants out of their bases in most of the other ones.
The government has been pursuing peace talks with the Pakistani Taliban, but the country's powerful military remains hesitant about the move.
Senior military officials said Wednesday's air strikes were launched after they had "confirmed intelligence information about hideouts of the militants and their top commanders".
Although they did not name the targeted commanders, officials said the strikes were aimed at those involved in recent attacks against Pakistani armed forces and Pakistani soldiers.
At least nine soldiers were killed and several critically wounded by a roadside bomb in the region earlier this month.
It is not possible to confirm the details of Wednesday's attacks because independent media are unable to access North Waziristan.
But local residents reported dozens of homes being flattened.
"It was around 3am in the morning when I heard huge explosions," tribesman Naseeb Gul told Reuters news agency by telephone.
"I saw four helicopters flying over the area and hitting some villages."
There have been similar air strikes since the beginning of the year, but this operation appears to have been the largest in a while, reports the BBC's Kim Ghattas from Islamabad.
She says it will further complicate efforts by the government to pursue peace talks with the Pakistani Taliban.
The process stalled after one round of negotiations in February, and a 40-day ceasefire between the two sides came to an end in mid-April.
Tens of thousands of Pakistanis have been killed since the Pakistani Taliban began their insurgency against the state in 2007.