A roadside bomb killed at least three Pakistani soldiers and wounded three others on Monday in the Waziristan tribal area bordering Afghanistan, security officials said.
The soldiers were on patrol in the hamlet of Ladha in South Waziristan, clearing the route and checking for mines ahead of a military convoy when an improvised explosive device (IED) exploded.
"Three soldiers embraced martyrdom and three others were wounded," a senior security official told AFP.
Another security official confirmed the blast and casualties.
Once notorious as a bastion of Tehreek-e-Taliban and Uzbek fighters, Ladha was reduced to a shell of damaged buildings, piles of rubble and a ruined paramilitary fort after the military launched an operation in 2009.
Since US Navy SEALs found and killed Osama bin Laden in Pakistan last month, American officials have been increasing pressure on Islamabad to launch an offensive in neighbouring North Waziristan to destroy militant sanctuaries.
Last week, Pakistani army chief of staff General Ashfaq Kayani urged people in North Waziristan "to evict all foreigners from their soil and take charge of their land and destiny once again".
Washington has called Pakistan's semi-autonomous tribal belt the most dangerous place on Earth and the global headquarters of Al-Qaeda, where Taliban and other Al-Qaeda-linked networks have carved out strongholds.