**A Pakistan army offensive against al-Qaeda and Taliban strongholds in South Waziristan has entered its second day with dozens of casualties reported.**A BBC correspondent in the region says there is a stalemate as 30,000 Pakistani troops, backed by tanks and artillery, encounter stiff resistance.
The army operation - the biggest for six years - comes after weeks of air strikes against militant targets.
Thousands of refugees are streaming into camps just outside the area.
There have been several co-ordinated Taliban attacks in recent days, killing more than 150 people in cities across Pakistan.
AT THE SCENE
Syed Shoaib Hasan, BBC News, South Waziristan borderThe fighting in South Waziristan is fierce and it is intense. Local administration officials say the Taliban are resisting fiercely as troops try to push into their territory.
Dozens of casualties have taken place, they say, and both sides are using heavy weapons.
Meanwhile locals from South Waziristan are facing great difficulty in leaving the area. All roads have been blocked by the military which is using them to transport ammunition and arms into the heart of the battle.
The transport and communication network has been effectively crippled. The casualties are now expected to rise as the terrain gets difficult for ground troops to operate in against the battle-hardened Taliban.
Eyewitness: At the edge of war
Dozens of casualties have already been reported by local officials as both sides used heavy weapons.
The bodies of three Pakistan soldiers were taken to the northern town of Razmak. There have also been unconfirmed reports of militant deaths.
Nearly all communications in the region were down after the Taliban destroyed a telecommunications tower at Tiarza, local officials said.
Reports from the area are sketchy as it is difficult and dangerous for foreign or Pakistani journalists to operate inside South Waziristan.
Aerial bombardments in the 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.
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
Pakistanis reflect on offensive
Thousands of civilians have fled South Waziristan in anticipation of the offensive.
Aid agencies say that many more are expected to flee but the tough terrain and the Taliban’s grip on the area will present difficulties.
Transport has been difficult as roads have been blocked by the military.
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.
On his way to South Waziristan, he passed several army convoys on the road.
The mobilisation came a day after Pakistan Prime Minister Yusuf Raza Gilani held a meeting of the country’s senior political and military leadership.
Lengthy planning
Recent militant attacks were seen as an attempt to divide public opinion, but they appear to have strengthened the resolve of the government, which says the Taliban must now be eliminated, our correspondent added.
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.
It also has numerous training camps for suicide bombers.
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