An official said no one has immediately claimed responsibility for the explosion, late on Friday, near Shakai, a town in South Waziristan.
He said the wounded, two of them in a critical condition, were being treated at a military hospital.
Another official, who also did not want to be named, said troops had launched a search for those who planted the mine, and several local tribesmen were being questioned.
No army spokesman was immediately available for comment, but similar attacks against Pakistani forces are common in the region, where Pakistan has deployed thousands of troops to capture al-Qaida-linked local and foreign fighters.
South Waziristan has been the scene of dozens of military raids on fighter hideouts since US-led forces overthrew the Taliban government in neighbouring Afghanistan after the 11 September 2001 attacks in the United States.
Pakistan, a key US ally, has asked local leaders to evict foreign fighters from their regions.