At least 6 security men were injured in a roadside bomb attack on their vehicle in Pakistan's South Waziristan tribal region on Tuesday, the army said.
The vehicle of paramilitary Frontier Constabulary was hit by a landmine in South Waziristan region, the army's inter-services of public relations said.
Two injured are in critical condition, it said.
No group claimed responsibility for the attack.
In the neighboring North Waziristan, clashes erupted between the security forces and militants suspects, according to local TV channel reports.
The security forces launched operation after the suspected militants fired on them, and a vehicle of the suspects was destroyed in firing from a military gunship helicopter in Khwaja Wali area of North Waziristan, reports said.
Violence has escalated in Pakistan since early July, especially in the tribal areas bordering Afghanistan and North West Frontier Province, where a series of attacks left over 100 people killed.
Armed tribal elders in North Waziristan two weeks ago announced the scrapping of a peace deal reached with authorities in September 2006 and threatened to launch more attacks on security personnel in the region.
Three security officials and four civilians were killed by militants in northwest Pakistan's North Waziristan tribal region on Monday in two separate incidents.