Islamabad - At least 20 people were killed and dozens injured in overnight clashes between tribesmen and followers of a radical cleric in a Pakistani tribal area bordering Afghanistan, media reports said.

The fighting between the militiamen of Lashkar Islami, or the Army of Islam, and the tribesmen began late Wednesday and continued Thursday morning in the Khyber Agency.

The groups targeted one another's positions in the mountains with rockets and mortar shells, Geo news channel reported.

Lashkar Islami is lead by firebrand cleric Mangal Bagh, who follows the puritanical Deobandi form of Sunni Islam. The leadership of Afghanistan and Pakistan's Taliban movement belongs to the same sect.

He has tried to enforce strict Taliban-style Islam in the region, provoking the tribesmen.

The highway between Pakistan and Afghanistan was closed because of the fighting, leaving the supply route for NATO forces cut off.

Pakistan's tribal areas are safe havens for numerous armed Islamic groups as well as al-Qaeda militants and Taliban fighters who have launched cross-border attacks on international forces in Afghanistan. (dpa)