MIRAN SHAH, Pakistan (AP) _ A bomb ripped through a car in Pakistan's northwestern tribal region on Sunday, killing two tribesmen, an official said.

The explosion occurred before dawn on a road near Khushali Torikhel, a village about 15 miles east of Miran Shah, the main town in the North Waziristan tribal area, government official Maqsood Hassan said.

The two men were traveling to the village when the explosion occurred, Hassan said.

There was no immediately claim of responsibility and Hassan said ``we are investigating to determine whether the two men were carrying the bomb in the car or somebody threw it at them.''

Local tribesmen often carry rifles and other heavy weapons for security.

Islamic militants are also active in the region, which borders Afghanistan. The fighters have been blamed for attacks against pro-government tribal elders in the past.

Pakistan is a key ally of the United States in the war against terrorism and it has deployed thousands of troops to North and the neighboring South Waziristan tribal regions to track down Islamic militants.