The Pakistan army has launched an air attack on what it believes to be a camp for suspected fighters in Waziristan, a tribal area bordering Afghanistan.
Major-General Shaukat Sultan, a spokesman for the military, said between 25 and 30 suspects were present at the time of the attack on Tuesday.
"The operation was carried out at around 6:55am (01:55 GMT) in Zam Zola in South Waziristan, based on information that 25 to 30 miscreants, including foreigners were present there," Sultan said.
He said missiles were fired at mud-walled compounds housing the suspects.
Helicopter gunships were then deployed to complete the operation. "I can't tell you the exact number of casualties, but most of them were killed," Sultan said.
While the army and a senior local official said the dead were fighters, and included some foreigners, a resident said the slain men were in fact Afghan labourers.
Kamal Hyder, Al Jazeera's correspondent in the region, said he had received unconfirmed reports that most of those killed were "innocent civilians" in the densely-wooded Zam Zola area. He said people were still being dug out.
He said that he also had unconfirmed reports that the attack came from Afghanistan, and had possibly involved American aircraft.
Pakistan's army insists that the raid was launched by its own attack helicopters.
The south of Waziristan has long acted as a refuge for the Taliban and al-Qaeda, despite an army campaign that began in late 2003 to clear them out.
The army later struck a peace deal, but fighters linked to the Taliban grew in influence in the semi-autonomous tribal region, actively recruiting men and boys to fight in Afghanistan.
Last September, the government of General Pervez Musharraf struck another peace deal with tribal elders in neighbouring North Waziristan. Afghan, Nato and US forces in Afghanistan are concerned that this accord will also result in pro-Taliban and al-Qaeda elements gathering in strength.
Pakistan has been trying to find ways to isolate the fighters in Waziristan as it has lost of hundreds of troops in the fighting and wants to reduce the risk of inducing a wider conflict in the tribal areas.