PESHAWAR, Pakistan- A suicide attack in the main town in Pakistan's northwestern Swat valley Sunday left 14 policemen dead, officials said, a month after the army claimed the area had been cleared of Taliban.

"The policemen were being given training in Mingora town when a suicide bomber entered the ground and blew himself up near the recruits, killing 14 of them," Swat police chief Qazi Ghulam Farooq told AFP.

A senior administration official, Ateef-ur-Rehman, confirmed the attack and said there were a number of casualties, adding police had been put on high alert against more attacks.

Another local senior police official, Mohammad Idrees, said that a curfew had been imposed in Mingora, adding troops and police were patrolling the town and people quickly shut their businesses in fear of more bombings.

It was the first major attack in Mingora since the military claimed last month to have cleared the valley of Taliban militants, paving the way for residents who had fled the area to avoid the fighting to begin returning home.

Pakistan in April launched a punishing military offensive against the Taliban in the northwest, targeting the rebels in the districts of Swat, Buner and Lower Dir after the militants advanced closer to the capital Islamabad.

The push forced 1.9 million civilians from their homes, most seeking refuge with relatives and the rest packing into refugee camps, creating a humanitarian crisis for impoverished Pakistan.

Last month, Prime Minister Yousuf Raza Gilani announced that the military had "eliminated" extremists in the northwest and according to government and UN statistics, 1.6 million displaced people have returned home.

Gilani's government has announced steps to reconstruct property destroyed during the punishing military operation and action to alleviate poverty in the area under a comprehensive package.

Swat slipped out of government control after radical cleric Maulana Fazlullah mounted a violent campaign in which his followers beheaded opponents, burnt schools and fought against government troops to enforce sharia law.

Pakistan says more than 1,930 militants and over 170 security personnel have been killed in the offensive, but the death tolls are impossible to verify independently.

The military has now turned its attention to the lawless nearby tribal belt, the heartland of Pakistan's umbrella organisation Tehreek-e-Taliban Pakistan (TTP), which is allegedly linked to Al-Qaeda.

But skirmishes continue in Swat and Buner, raising fears that the Taliban are regrouping in the mountains, a tactic militants have adopted after government offensives in the past.

Pakistani authorities have also advocated the establishment of local militia in the northwest to try and keep the Taliban at bay, amid reports that the Islamist fighters have simply melted into the mountains.

Fazlullah meanwhile remains at large. -AFP