Pakistan says a fierce military offensive has captured dozens of suspected al-Qaida militants, and the operation is continuing in a remote mountainous region near the Afghan border. Military officials say the militants may include a senior Chechen or Uzbek leader.

Military officials say Pakistani troops have captured more than 100 suspected terrorists since the fighting began on Tuesday in the tribal region of South Waziristan. Those detained include foreigners and their local supporters.

Reports have suggested a top leader of al-Qaida, possibly the network's Number two leader, Ayman al-Zawahiri, is trapped in the region.

Military spokesman Major General Shaukat Sultan refuses to confirm these reports.

"The possibility of a high-value target being present here cannot be ruled out, but one can't say who could he be," he said.

The commander of the operation, Lieutenant General Safdar Hussain, told reporters Saturday that the suspected senior al-Qaida member in the region is most probably a Chechen or Uzbek militant leader.

Military officials believe a large number of suspected al-Qaida militants are still holed up in heavily fortified compounds, and say gunmen are using automatic weapons, mortars, rockets and grenades. General Sultan describes the fighting.

"From the type of resistance that we are getting, from the type of the quantum of fire that we are getting, a fair assessment says that the militants over there could be anything between 300 to 400 (in number)," said General Sultan.

Pakistani ground troops, backed by helicopter gunships, are relentlessly pounding the militants' positions. Senior security officials say Chechens, Uzbeks, Arabs and local tribesmen are fighting the government forces.

Local officials say a large number of ethnic Uzbek Islamic militants, led by Qari Tahir Yaldash, have recently been seen in the region. The group was allied with neighboring Afghanistan's former Taleban government, which harbored the al-Qaida terror network and its leadership.

General Sultan says no American troops are taking part in the operation, which has left at least 40 people dead, including 17 government soldiers.

"There are a few Americans present, about a dozen or so, who are assisting Pakistan in intelligence, in surveillance, satellite imaging, but on the ground there are no American forces," he said.

Pakistan's semi-autonomous region of South Waziristan has long been considered the hiding place for fugitive al-Qaida members. The region borders Afghanistan, where the U.S.-led coalition has mobilized forces to stop militants from escaping the Pakistani offensive.