The explosion -- the latest in a series of land mine incidents -- occurred in the Kurram Agency tribal region on the Afghan frontier, local broadcaster Dawn News reported.

The van was carrying passengers to nearby Parachinar, the only Shia Muslim-majority city in Pakistan's tribal region.

Army spokesman Maj. Gen. Asif Ghafoor said in a statement that a military helicopter was flown to the site to transport the injured to Peshawar, the capital of the Khyber Pakhtunkhwa tribal region.

No group has so far claimed responsibility for the attack, but Taliban militants have been active in the region for more than a decade.

Kurram Agency is one of seven tribal regions in Pakistan and Parachinar has been struck by major bomb attacks targeting Shias in recent months.