A suicide bomber targeting government troops blew up his explosives-laden car in northwestern Pakistan early Friday, killing two people and wounding more than 30, officials said.
The attacker struck at a checkpost near a road tunnel in the lawless town of Darra Adam Khel in North West Frontier Province.
"It was a suicide attack, the bomber rammed his vehicle into a security camp outside the tunnel," highway official Shakil Ahmed told AFP by telephone.
Local police officer Fazal Ayaz said two civilians were killed and 31 others including 29 soldiers from the paramilitary Frontier Corps wounded.
Hospital officials said five of the soldiers were in serious condition.
The attack came after troops arrested four militants including a Taliban commander in a raid in the nearby garrison town of Kohat on Thursday, residents said.
Darra Adam Khel is known for its weapons bazaar and illegal arms factories.
Pakistan used artillery and helicopter gunships to dislodge militants who seized control of the tunnel, situated between Peshawar and Kohat, in January this year.
Security officials say Darra Adam Khel has recently become a stronghold of the banned Sunni Muslim extremist group Lashkar-e-Jhangvi, which is said to have links to Al-Qaeda.
Pakistan troops are engaged in an operation against Taliban and Al-Qaeda militants in the tribal Bajaur region on the border with Afghanistan amid a surge in militant violence.