A pro-Taliban cleric's militant followers on Saturday clashed with security forces at several places in Swat valley of northwest Pakistan leaving up to 15 people dead, a day after troops backed by helicopter gunships attacked a seminary run by him.

A dozen security personnel were among the 15 people killed in the clashes, reports said. However, officials confirmed only five deaths, including two civilians.

The skirmishes erupted after security forces attacked Maulana Fazlullah's sprawling madrassa at Imamdheri, three kilometres from Mingora, the headquarters of Swat district in North West Frontier Province.

Three militants were killed by troops on Friday near the seminary, and the ultras retaliated by abducting and beheading four paramilitary troopers and a policeman in the nearby Matta area, the reports said.

There were intermittent exchanges of fire between security forces and militants holed up in the seminary near the Swat river.  The militants also carried out a number of attacks on security forces at Matta, Kanju and other places, sparking gun battles with Frontier Corps personnel and police.

Some 100 militants surrounded the police post at Charbagh sub-district. They exchanged fire with nine policemen holed up in the post, officials said.

Militants also attacked and set on fire the house of Matta district's nazim though there were no casualties in the incident as the official and his family had shifted to Islamabad. There were also reports of heavy exchanges of fire between rebels and security forces in Kabal.

Three policemen were abducted by militants at Tall in Hangu district while two more headless bodies of security personnel were found in Matta, Dawn News channel quoted sources and witnesses as saying.

The clashes have caused tension in the region and hundreds of people have fled the Swat valley.

Fazlullah, who heads the outlawed Tehrik Nifaz-e-Shariat Mohammadi that sent hundreds of fighters to Afghanistan, has reportedly shifted to Kohistan, 200 km from Mingora.

His spokesman Sirajuddin said the militants would defend the seminary in Imamdheri, the headquarters of the radical cleric known as "FM Maulana" for his fiery broadcasts from an illegal radio station.

 Amidst reports that a jirga or tribal council had been convened to put in place a ceasefire, Sirajuddin said the local administration had not contacted the militants for a truce. He also renewed Fazlullah's demand for the  imposition of shariat or Islamic law in the region.

Thousands of paramilitary troops were deployed in the Swat area earlier this week to counter the activities of Fazlullah and to restore the writ of the local administration in 59 villages where the cleric's armed followers are running a parallel government.

The Army has said it is on standby in the Swat region and has not yet launched any operation.