Pro-Taliban fighters have beheaded 13 civilians and security officers in northwest Pakistan after government troops launched an assault on Maulana Fazlullah, a pro-Taliban cleric.

Officials said the beheadings took place in the Swat valley in the North West Frontier Province (NWFP).

The region is where soldiers had clashed with fighters loyal to the cleric, who has been driving a campaign to introduce pro-Taliban laws.

The military deployed more than 2,000 troops to the region in an effort to crack down on attacks launched against government leaders and security forces.

According to Badshah Gul Wazir, the provincial home secretary, the fighters had abducted three police and three paramilitary officers shopping at a bazaar in Matta, on the outskirts of Swat, and had beheaded all of them.

He said the bodies and severed heads were then paraded in front of local residents to scare them.

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Also on Friday, seven civilians were seized from a minibus by the fighters who then executed them, Sharif Virk, the provincial police chief, said.

"They were also slaughtered by terrorists who accused them of collaborating with the government forces," he said.

Continued battle

Maulana Fazlullah heads a group called the Nifaz al-Shariat Mohammadia Movement (TNSM).

Muslim Khan Rashid, a member of the Shura council of the TNSM said the killing of the officers came in retaliation for the storming of the Red Mosque in Islamabad, the Pakistani capital.

He "regretted" the slaughter of the security officers but blamed government forces for provoking the attack.

Khan said: "We are fighting because the government forces have attacked us."

"We are only demanding enforcement of Sharia [Islamic laws] in the district and withdrawal of the army and paramilitary from the region."

Fighters had reportedly kidnapped the men on the outskirts of Swat in an apparent response to an attack on the Imam Dheri village, a stronghold of Fazlullah, where security forces and fighters exchanged fire using rocket-propelled grenades, mortars and other weapons.

The fighting came after a blast hit a security forces vehicle in Swat, killing at least 20 people and wounding another 35.

Al Jazeera's Sohail Rahman, reporting from Swat, says that Fazlullah has not been seen for a few days, as a build up of military personnel in the region enters its fourth day.

Troop deployment into the area continues [AFP]

He said: "There has been an ongoing firefight between fighters and the military, and the fighters seem solid and confident with their arsenal of weapons, ranging from AK-47s and surface-to-air missiles."

'Mullah Radio'

Violence first erupted in Swat in July, when fighters had launched revenge attacks on the army after government troops stormed the Red Mosque.

Fazlullah is known as Mullah Radio for his fiery radio speeches in which he calls for the imposition of Islamic Sharia law and for attacks on Pakistani security forces.

Pakistan has around 90,000 troops in the tribal belt combating Taliban and al-Qaeda fighters who fled Afghanistan in 2001, as well as their Pakistani supporters.

More than 250 people, including about 50 soldiers, were killed in battles in the tribal region of North Waziristan earlier this month.