Islamabad (PTI): At least 20 people were killed and dozens injured in overnight clashes between tribesmen and militant followers of a radical cleric in Pakistan's northwestern Khyber Agency bordering Afghanistan.

Fighting erupted between Lashkar-e-Islam cadres led by cleric Mangal Bagh Afridi and Kooki Khel tribesmen on wednesday following three days of tension.

The two sides have been at loggerheads since the Kooki Khel tribe refused to accept 30 demands made by Afridi, including an end to "immoral and un-Islamic activities".

Twenty people were killed and dozens injured in the clashes, Geo News channel reported. Both sides targeted each other's positions with heavy weapons like rockets and mortars. Several mortar shells landed in the North West Frontier Province capital of Peshawar.

Official sources said 17 personnel of the Khasadar militia were also kidnapped from a check post by Afridi's followers. The Lashkar-e-Islam chief gave a deadline for security forces and the political administration to vacate Jamrud, the main town of Khyber Agency, by 4 pm today.

Reports suggested that the security forces could launch a major operation in Khyber Agency to quell the activities of Lashkar-e-Islam militants. The Frontier Corps shelled militant positions but there were no reports of casualties.