WANA, Pakistan - Pakistan's military has arrested more than 100 suspects in a five-day assault on militants holed up in mud fortresses along the border where al-Qaida No. 2 Ayman al Zawahri is believed trapped, a commander said Saturday.

Those detained included foreigners and the local Pashtun tribesmen who have been sheltering them, said Lt. Gen. Safdar Hussain, who is in charge of the sweep. Hussain said 400 to 500 militants are believed to still be fighting from within the heavily fortified compounds, using mortars, AK-47s, rockets and hand-grenades in a face-off with troops.

"These people have been here for a long, long time. They are extremely professional fighters," he said. "They have tremendous patience before they open fire."

The military showed journalists 40 prisoners, all blindfolded and with their hands tied, who were sitting under heavy guard in the back of a military truck in Wana, the main town in the tribal South Waziristan region, where the battle was raging.

The army also displayed the body of one suspected militant wrapped in a white blanket.

Hussain said troops were convinced the compounds held a "high-value" target, but he said they had no confirmation the man was al-Zawahri.

He said the militants attacked his troops from all directions during an initial assault Tuesday in which the bulk of the 17 army casualties were killed.

"It's practically like chasing a shadow," he said. "The resistance we're facing is tremendous."

As he spoke, Cobra attack helicopters hovered overhead, some swooping toward the battle zone.

Brig. Mahmood Shah, the chief of security for tribal areas in northwestern Pakistan, said the fierce fighting, heavy fortifications and other intelligence led authorities to believe al-Zawahri might be among the militants. He said authorities had gotten "one or two reports" that the al-Qaida No. 2 had been in the area in the recent past.

An Afghan intelligence official with connections in Pakistan's tribal region also told AP that al-Zawarhi was believed in the area of the Pakistan operation, in South Waziristan.

Osama bin Laden is believed farther north, in North Waziristan, across from the region of the Afghan border city of Khost, the official said. There was no firm intelligence on the terror chief's exact location, however.

The fighting has forced an exodus of thousands of terrified civilians, who have poured out of the battle zone deep in South Waziristan. Many have taken refuge in Wana, but there were indications the battle was following close on their heels.

Loud explosions and gunfire could be heard early Saturday in Gangikhel village, a hamlet of simple mud dwellings just west of Wana. Previous fighting in Kaloosha, Azam Warsak and Shin Warsak was closer to the border with Afghanistan.

Shah told AP that some of the prisoners had already been taken for interrogation to the provincial capital, Peshawar.

Security officials said the men included Pakistanis, Arabs, Chechens, Uzbeks and ethnic Uighurs from China's predominantly Muslim Xinjiang province, where a separatist movement is simmering. No senior al-Qaida leaders were believed to be among them, but authorities hoped they would provide a better picture of the terrorists' heavily fortified lair.

At least 80 ethnic Uzbek Islamic militants, led by Qari Tahir Yaldash, a Taliban ally and deputy of slain Uzbek leader Juma Namangani reportedly are in the Waziristan region. Namangani was killed during the U.S.-led coalition's assault on Afghanistan that began in late 2001.

"Our people are interrogating them to determine who these terrorists are," Shah said. "Some of them are foreigners."

Fighting stopped Friday evening, but troops later began firing artillery guns, an intelligence official in Wana said on condition of anonymity.

Army spokesman Maj. Gen. Shaukat Sultan said the Pakistani forces were joined by "a dozen or so" American intelligence agents in the ongoing operation. U.S. satellites, Predator drones and other surveillance equipment hovered overhead.

Sultan put the number of troops killed in the operation at 17, most in the disastrous initial assault on Tuesday. But other military and intelligence officials said many more had died in the heaviest fighting on Thursday and Friday, and about a dozen soldiers are missing and feared taken hostage.

Jawed Ludin, a spokesman for Afghan President Hamid Karzai said U.S. and Afghan troops captured "semi-senior" terrorist leaders on their side of the border in recent days, though the American military did not confirm that. Ludin declined to give any details of who might be in custody.

Interior Minister Faisal Saleh Hayyat told AP that authorities hoped to wrap up the operation by Sunday afternoon, but Shah said the going was slow, with soldiers proceeding cautiously from house to house.

"We are trying to avoid collateral damage to the civilian population. It might take some time," he said.

Sultan said the Pakistani forces had surrounded an area of 20 square miles centered on Shin Warsak, using an inner and outer cordon of troops numbering a "couple of thousand."