Military spokesman Major-General Shaukat Sultan said an operation targeting Abd Allah Masud was in progress in South Waziristan, with locals specifying the mountains near Spinkay Raghzai.
   
Four gunship helicopters were hovering over the area and spraying it with machinegun fire, while the army was pounding the location with artillery, locals added.
   
The air attack came as some government troops were put under a virtual siege in a shoe factory in the area.

Costly rescue attempt
   
Pakistan has vowed to hunt down Masud, who is believed to have arranged the abduction of two Chinese engineers working on a dam in South Waziristan on 9 October - straining ties with Beijing, one of Islamabad's closest allies.
   
One of the hostages and all of the kidnappers were killed after army commandos launched a rescue operation last week.
   
South Waziristan has been the scene of fierce clashes between security forces and tribal groups claimed to be sympathetic to al-Qaida.

The US military commander in Afghanistan, Lieutenant-General David Barno, said last month that al-Qaida leader Usama bin Ladin was most likely to be hiding in Pakistan - a claim denied by Pakistan's Lieutenant General Safdar Husain.
   
But Husain, the Pakistani military commander in the region, said on Tuesday that bin Laden was unlikely to be hiding in the tribal zone.