The military said the camp was located near Dila Khula, a South Waziristan village about 15 miles northeast of the region's main town, Wana.
"There were confirmed reports of training activity being conducted by foreign elements including Uzbeks, Chechens and a few Arabs," the military said in a statement. "These trained terrorists were indulging in sabotage and terrorist acts in the country."
Army spokesman Maj. Gen. Shaukat Sultan told the private ARY television channel that 50 people were killed and 90 percent of them were foreigners. He said the camp was totally destroyed and all the people there were believed killed.
Another senior military official said all the dead were killed in airstrikes.
"Troops have now moved into the area. They have started a search and found 50 bodies," he told The Associated Press on condition of anonymity.
Sultan said the men had been involved in terrorist acts inside Pakistan, but gave no details. He said they were not in any way connected to suspected Chechen and Arab militants whoin southern Russia earlier this month. At least 330 people — many of them children — died in the end to that siege.
"We came to know about this camp after investigations into recent terrorist attacks in Pakistan," Sultan said.
A large number of Central Asian and Arab militants are believed to be living in the tribal areas bordering Afghanistan. Many came to fight alongside U.S.-backed Afghan mujahideen against the Soviet Union in the 1980s, and some never left.
Pakistan has frequently overstated the scope of its military operations, claiming to have captured or killed foreigners that turn out to be local tribesmen, or to have zeroed in on top al Qaeda men who never materialize.
Alam Khan, a resident of Ladha, a village near Khunkhela, told The Associated Press by phone that three other nearby villages were also hit in the operation. He said he saw at least two jets and about 10 army helicopters flying over the scene during the fighting, which lasted about two hours.
Dust and smoke could be seen rising from houses in the villages, Khan said. He had no word on casualties.
Pakistan's army has launched frequent attacks in North and South Waziristan to flush out Islamic militants. The area is considered a possible hideout for Osama bin Laden, though there is no hard evidence of his whereabouts.
The bombing came after a land mine injured three soldiers in Wana on Wednesday, prompting a firefight that left seven tribesmen dead, an intelligence official said Thursday.
Pakistan, an ally in the U.S.-led campaign against terrorism, has deployed tens of thousands of troops along the Afghan border to fight al Qaeda and Taliban fighters operating there.
Pakistan's powerful ISI intelligence service once backed the Taliban, but after the Sept. 11 attacks President Pervez Musharraf allied himself with the Bush administration.
Pakistan has been rewarded with the suspension of sanctions imposed after a nuclear test in 1998 and Musharraf's bloodless coup against a democratic government in 1999.
Musharraf was the target of at least two assassination attempts last year.
Over the summer, Pakistani police and security agencies have detained about 30 terror suspects, including Ahmed Khalfan Ghailani, a Tanzanian with a $25 million bounty on his head for his role in the 1998 bombings of U.S. embassies in East Africa.
Ghailani was arrested along with 13 other foreigners during a raid in the eastern Pakistani city of Gujrat on July 25.
Pakistani officials have said that information from Mohammed Naeem Noor Khan, an al Qaeda computer engineer who was captured on July 13 in Lahore, led to Ghailani's arrest and to about a dozen other arrests in London.
Computers from Khan and Ghailani contained photographs of potential targets in the United States and London's Heathrow Airport, as well as pictures of underpasses that run beneath several buildings in London. That suggested al Qaeda might be planning terrorist attacks — although it wasn't clear how recently the photos were taken.