PESHAWAR, Pakistan, Oct 9, 2008 (AFP) - Pakistani fighter jets and helicopter gunships Thursday destroyed a Taliban militant facility in the restive northwest, inflicting heavy casualties, security officials said.

The air strike targeted a militant stronghold in Piochar, a village in the Swat valley, a former tourist area once dubbed the 'Switzerland of Pakistan' where troops have been battling extremists since last year.

'Helicopter gunships and jets targeted militant strongholds in Piochar, inflicting heavy casualties on them, but a count was not available immediately,' a security official told AFP.

'The successful air strike destroyed the targeted militant facility completely,' the official said, requesting anonymity.

Separately, five civilians, including women and children, were killed when a shell hit a house in the Matta district of Swat during clashes between troops and insurgents, another security official told AFP.

It was not clear which side fired the fatal shell.

The mountainous Swat valley was until last year where many Pakistani city dwellers went for their annual holidays and it featured Pakistan's only ski resort.

But it has been turned into a battleground since pro-Taliban cleric Maulana Fazlullah launched a violent campaign to enforce harsh Islamic Sharia law in the region -- while the ski resort has been burnt down.

Taliban militants set ablaze a government-run primary school late Wednesday in Swat's Kabal district, the stronghold of Maulana Fazlullah, security officials said.

Pakistan's military spy chief was on Thursday briefing lawmakers on the threat posed by Al-Qaeda and Taliban militants, in the second day of a rare intelligence briefing held behind closed doors in parliament.