Pakistan's envoy to Afghanistan, who went missing in the Khyber Agency four days ago while on his way to Kabul, is not in the restive tribal area along the frontier, a top radical Islamic leader has claimed.

Lashkar-e-Islami chief Mangal Bagh, who wields considerable influence in the Khyber Agency, said Ambassador Tariq Azizuddin is not in the tribal region and it would be unjust for the government to conduct any sort of military operation in the agency to locate him.

The radical leader also told Dawn News channel that Azizuddin had not been kidnapped from the Agency, contrary to media reports.

Pakistani security forces on Thursday launched a crackdown against tribesmen in the Khyber Agency, after they failed to trace Azizuddin, who is believed to have been kidnapped in the region on Monday.

North West Frontier Province Governor Owais Ghani said Azizuddin is in the Khyber Agency as authorities have found important clues there.

Political authorities said the search was currently focused on the Peera Valley and Zakakhel areas. As part of the crackdown, security forces have arrested 12 tribesmen. Ten Khasadar militia, manning a check post passed by Azizuddin's car, have also been detained on charges of negligence.

Reports said the envoy's car was not stopped at the check post even though some locals were spotted sitting in the vehicle. Security has been increased at all border check posts, additional security personnel have been deployed in the area and patrolling has been stepped up along the Afghan frontier.

Azizuddin was traveling by car from his home in the NWFP capital Peshawar to Kabul when he went missing with his driver and a security guard in the Khyber Agency.

The government convened a jirga or council of tribal elders on Thursday and urged them to trace the envoy.

The foreign ministry has said that no group has contacted the government to claim responsibility for abducting Azizuddin, one of Pakistan's highest-ranking diplomats.

Foreign Office spokesman Mohammad Sadiq has also said that the envoy is alive. The Pakistani Taliban, led by Baitullah Mehsud, has denied any role in the incident.