WANA: The army shelled militant hideouts in Pakistan's northwest tribal belt Tuesday, where forces are believed to be on the brink of an all-out onslaught to crush the Taliban, officials said.

Artillery struck insurgent hideouts in districts of South Waziristan, a northwestern tribal region and stronghold of Pakistani Taliban chief Baitullah Mehsud.

‘Security forces used heavy artillery to pound militant hideouts. We have reports that several miscreants have been killed but we do not know the exact number,’ said an intelligence official in Peshawar.

A government official based in the area confirmed the strikes, which began overnight and continued into early Tuesday, telling AFP: ‘They are targeting Kotkai, Spinkai Raghzai and Srarogha areas.’

Residents also reported shelling in the area, which ended in the morning.

‘There is heavy firing since midnight — we can hear it,’ Spinkai Raghzai resident Aftab Wazir told AFP.

Security forces are already locked in a seven-week campaign against militants in three northwestern districts, and a governor late Sunday announced a ‘full-fledged’ second front along the mountainous tribal belt.

North West Frontier Province governor Owais Ahmad Ghani vowed to track down Mehsud, blaming him for a string of recent deadly bomb attacks.

The army has so far stayed silent on any new campaign in the tribal areas and it is not clear when an all-out offensive would begin. It has officially confirmed only some retaliatory strikes in and around South Waziristan.

New York-based watchdog Human Rights Watch on Tuesday urged the military to do all it could to avoid civilian casualties in any fresh offensive.

The group said that during the ongoing Swat campaign, many families have been trapped in the conflict zone, without being given ample chance to flee.

‘The Taliban's disregard for civilian life should not be mimicked by the Pakistani military,’ said the group's Asia director Brad Adams.

‘For warnings of impending attacks to be effective in reducing civilian casualties, the army needs to allow civilians time to evacuate and recognise that not everyone will be able to leave.’

Security forces launched their offensive against Taliban fighters in and around Swat valley on April 26, after the insurgents flouted a peace deal and advanced to within 100 kilometres of Islamabad.

About two million people have fled their homes and escaped to safer parts of Pakistan since the offensive began, and residents and local officials have said people are also on the move out of Waziristan, fearing an imminent attack.