KOHAT, Aug 29: Two drivers were killed and 39 others, 36 security personnel among them, injured when a car blew up after a suspected suicide bomber driving it was shot dead by troops near the Kohat Tunnel on Friday.

Official sources said troops had attacked the car with a rocket in front of an army base camp in Darra Adamkhel Frontier Region.

The security personnel first thought that it was an official vehicle, but became suspicious when they saw a bearded driver with long hair in green clothes.

All the injured security personnel, among them a colonel, were in their offices in the base camp.

Noor Sher of Karak and Haq Nawaz of Peshawar, drivers of a truck and a pick-up, were killed.

Sources told Dawn that the vehicle used in the explosion had been taken at gunpoint by militants four months ago in Darra Adamkhel from Nayyer Ahmed, manager of the company managing security at the tunnel.

It could not be ascertained whether explosives in the car or the rocket had caused the explosion.

Kohat District Coordination Officer Siraj Ahmed, who is also the political agent for the Frontier Region, said security personnel had probably thwarted an attack on the camp. Had the car entered the base camp it could have caused mayhem.

The injured personnel were taken to the Combined Military Hospital. Four soldiers was stated to be in critical condition.

Two more people -- Syed Baseer of Khadizai area and Kamran Ali of Alizai village -- were killed and another injured when security personnel opened fire at a suspicious car soon after the blast.

Militants also blew up three bridges on the Indus Highway.

Official sources said troops had killed and injured occupants of the car, which was going from Darra town towards Kohat.

The district coordination officer said the abortive attacks could have been planned in retaliation for the recent arrest of four top militants, including two Taliban belonging to the commander Tariq group. The suspects — Ajmal, Shah Zaman, Sayed Omar and Khalid — were arrested on Thursday.

With tension running high in Darra town, people have started leaving their homes and militants have gone into hiding.

Many families have moved to Peshawar amid reports that security forces based in Kohat were moving towards the tribal region.

Troops cordoned off Sheraki, Tor Chapper and Bosti Khel areas and did not allow people to leave their homes.

The Kohat Japan Friendship Tunnel has been closed over security concerns.

BRIDGES BLOWN UP: Militants blew up two bridges on the Indus Highway in Akhorwal and another in Zarghun Khel area.