Pakistani officials said the attack occurred at around midnight on Monday on a mountaintop post in the village of Sarbandki.
Unknown assailants fired rockets at the post east of Miran Shah, the main town in the unsettled tribal region of North Wazirisatan.
A government official said five soldiers were killed, but an intelligence official in the region said only that there were "several" casualties. Both spoke on condition of anonymity.
Pakistan has around 70,000 troops and paramilitary forces along its border with Afghanistan to weed out alleged al-Qaida and Taliban sympathizers.
The attack was the latest in a series of offensives against Pakistani forces in the North Warizistan region, a rugged mountainous area bordering Afghanistan.
Earlier on Monday, assailants had fired rockets at a security checkpoint and exchanged fire with troops west of Miran Shah, injuring three. That attack happened just three days after eight soldiers were ambushed and killed in an assault on another checkpoint.
Last month, a senior al-Qaida suspect from Egypt, Hamza Rabia, was killed in the area. Pakistan denied residents' claims that he died in a U.S. missile strike.