A roadside bomb struck a Pakistani military convoy close to the Afghan border on Monday, killing at least two soldiers, a security official said.
The attack took place near Wana, the main town of the Taliban heartland of South Waziristan.
"Two soldiers were killed and three others wounded when their vehicle was blown up by an explosive device planted along the road," the official said on the condition of anonymity.
Troops were moving to Wana from the nearby northwestern city of Dera Ismail Khan to expel militants from a local telephone exchange.
More than 7,000 phone lines have gone out of service in the district after the Taliban fighters took control of the exchange in recent days.
Government forces targeted militant positions after the roadside bombing, but there were no immediate reports of casualties.
South Waziristan is the stronghold of slain Pakistani Taliban chief Baitullah Mehsud, who was killed in a US missile strike on August 5.
The warlord, described as Pakistan's enemy number one and a key Al Qaeda facilitator, was succeeded by his close aide, Hakimullah Mehsud, who is no relation.
Al Qaeda and Taliban militants use the tribal district as a launching pad for attacking foreign troops in neighbouring Afghanistan.