A missile attack, possibly launched by US forces in Afghanistan, killed at least 32 pro-Taliban militants in a Pakistani tribal region near the border on Tuesday, Pakistani officials said.
The missiles targeted a suspected training base in a village near the mountainous Datta Khel district, 60 km (40 miles) west of Miranshah, the main town in North Waziristan, the officials, who spoke on condition of anonymity because they are not authorised to brief the media, said.
Intelligence officials said some foreigners were among those killed, raising the possibility that al-Qaeda fighters might have also been present.
North Waziristan is a known refuge for remnants of Osama bin Laden's network.
"There was a cluster of three houses and a tent which were hit. There were about 45 people in that area," a senior government official said.
Army spokesman Major-General Waheed Arshad said there had been an explosion in the area, but he denied it was caused by missiles and added that the army had not carried out any operations there either.
"It wasn't a missile attack," Arshad said, adding that initial reports suggested the explosion occurred while the militants were making a bomb.
Such explanations have been offered in the past when US forces in Afghanistan have launched strikes on targets in Pakistani territory.
The goverment is sensitive to any report of foreign forces carrying out operations in Pakistani territory or airspace.
According to intelligence officials and residents, however, a US pilotless drone aircraft carried out the attack at around 10:30 am.