The army has mobilised artillery and troops in the area
Taliban militants are putting up fierce resistance to the Pakistan army as it attempts to oust them from strongholds in the remote South Waziristan region.
The army say about 60 militants and five soldiers have now been killed.
It is the first official death toll since troops, backed by heavy artillery and air support, began attacking Taliban hideouts on Saturday.
Up to 20,000 people have fled the area in the past few days, and aid agencies say many more could be displaced.
The BBC's Syed Shoaib Hasan, reporting from Dera Ismail Khan, says civilians fleeing the area have complained that the government has made little provision to help them.
No clear picture
Thousands of people have fled the fighting in recent days
The military, mobilising from three directions, is controlling entry and exit points in the region.
Reports from the area are sketchy as it is difficult and dangerous for foreign or Pakistani journalists to operate inside South Waziristan.
Local residents in Tiarza say that troops have forced their way into the town, and are using helicopter gunships to attack Taliban forces in the hills around.
Soldiers are also reported to have taken ground around Spinkai Raghzai.
Troops established a checkpoint en route to Kotkai, the home town of Pakistani Taliban chief Hakimullah Mehsud, AFP reported.
But our correspondent says no clear picture has emerged about who has the upper hand at the moment.
There had been several co-ordinated Taliban attacks in the run-up to the offensive, killing more than 150 people in cities across Pakistan.
FORCES IN WAZIRISTAN
Pakistan army: Two divisions totalling 28,000 soldiers
Frontier Corp: Paramilitary forces from tribal areas likely to support army
Taliban militants: Estimated between 10,000 and 20,000
Uzbek fighters supporting Taliban: Estimates widely vary between 500-5,000
Security is tight in towns and cities throughout Pakistan in case the Taliban carry out revenge attacks.
Nearly all communications in the region were down after the Taliban destroyed a telecommunications tower at Tiarza, local officials said.
Aerial bombardments in the Makeen area, a stronghold of the Mehsud tribe and a key army target, were also reported by local officials and witnesses.
The ground operation comes after weeks of air and artillery strikes against militant targets in the region, which lies close to the Afghan border.
There is a huge army presence on the road between Tank and Dera Ismail Khan, says the BBC's Islamabad correspondent Shoaib Hasan, near South Waziristan.
The army has been massing troops near the militants' stronghold for months - ever since the governor of Pakistan's North West Frontier Province announced a ground offensive in South Waziristan on 15 June.
Pakistan's government has been under considerable pressure from the US to tackle militancy there.
North and South Waziristan form a lethal militant belt from where insurgents have launched attacks across north-west Pakistan as well as into parts of eastern Afghanistan
South Waziristan is considered to be the first significant sanctuary for Islamic militants outside Afghanistan since 9/11.
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