Pakistan is currently undergoing an all out attack on the tribal belt bordering Afghanistan, which is the alleged hideout of Osama bin Laden and other terrorists. On Tuesday its airforce pounded militant positions in North Waziristan, as fighting raged for a fourth day in the tribal region known as an al Qaeda and Taliban stronghold, according to the Pakistani army.

"We have received information from local tribal sources that 50 militants were killed," army spokesman Major General Waheed Arshad told local media. In the last three days, around 250 pro-Taliban militants and government troops have died in the heavy fighting. The private Geo and Aaj news channels quoted villagers as saying the airstrikes hit a busy market and that many civilians were killed and at least 150 people were injured.

The offensive was launched after insurgent ambushes of army convoys in North Waziristan late Saturday. In total, more than 200 insurgents and 45 soldiers died. Insurgents in the region and surrounding North-West Frontier Province (NWFP) have intensified attacks on security forces since commandos stormed the radical Red Mosque in Islamabad in July. More than 300 people, including 100 soldiers, have died in the attacks.

"They will not surrender. It's their terrain, it's their home, and they will fight until the end," said Rahimullah Yousafzai, an expert on Pashtun affairs, according to AFP. Pakistan still has around-90,000 troops in the area.

Thousands of people have fled from Mir Ali, a town in lawless North Waziristan district that President Pervez Musharraf has previously pinpointed as a den of Osama bin Laden's Al-Qaeda network. They left after 50 houses were damaged and the army placed the town under virtual curfew, residents said.

North Waziristan is inhabited by the Pashtun Wazirs and Daurs tribes. The region became part of Pakistan in 1947.