Although Lt. Gen. Safdar Hussain hedged on the identity of the senior figure, he said he still believed a "high-value" terrorist target remained in the trap and had not escaped across the border into Afghanistan.
The operation in the arid, rugged terrain of South Waziristan raged into its fifth day with no sign of surrender from 400 to 500 foreign fighters and local tribesmen facing a thunderous barrage of artillery by night and Cobra helicopter gunship fire by day.
Hussain said 5,000 to 6,000 Pakistani troops were deployed in Pakistan's largest anti-terror campaign, conducted across a 25-square-mile swath of territory within 10 miles of the Afghan frontier.
About 2,500 soldiers were fighting the militants and the rest conducting searches, he said. Pakistani officials said a dozen American personnel are helping with technical intelligence and surveillance.
"I would not rule out any possibility, but with this level of resistance, even after 48 hours (of bombardment), I believe the high-value target is still there," Hussain told about 40 journalists flown by Pakistan's military to this town about three miles from the battle.
He said the fighters were a blend of foreigners and members of the local Yargul Khel tribe, and that this was the first of a series of operations to clear the lawless tribal region of militants.
The military announced Saturday that more than 100 fighters had been detained, some of them sent to the provincial capital, Peshawar, for interrogation. It showed journalists about 40 captured fighters at a military base in Wana, the main town in South Waziristan. They were blindfolded and with hands bound, crammed into a military truck. The corpse of another militant lay wrapped in a white shroud in a military ambulance.
Security officials said prisoners under interrogation included Pakistanis, Arabs, Chechens, Uzbeks and ethnic Uighurs from China's predominantly Muslim Xinjiang province, where a separatist movement is simmering.
There have been reports that at least 80 ethnic Uzbek Islamic militants, led by Qari Tahir Yaldash - a Taliban ally and deputy of slain Uzbek leader Juma Namangani - 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," said Brig. Mahmood Shah, the chief of security for tribal areas in northwestern Pakistan. "Some of them are foreigners."
The military also showed journalists in Wana belongings and equipment seized from a Chechen fighter who was killed, including grenades, detonators, a traditional pakor hat and prayer beads. Also displayed were four locally made rifles, a dozen grenades, AK-47s and boxes of Soviet-era ammunition seized from tribesmen.
The Pakistani army has intercepted some radio conversations of militants inside the encampment, mostly in the Chechen and Uzbek languages and some in Arabic.
One radio intercept in Uzbek or Chechen said a man wounded when he tried unsuccessfully to flee the area in a vehicle on the first day of the operation would need "four men to carry him and 10 or 11 people to protect him," Hussain revealed.
That raised suspicion the man was important and "most likely Chechen or Uzbek, as the intercepts were in those languages," he said.
Al-Zawahri is Egyptian, and would be expected to have mostly Arabic-speaking protectors. But Hussain said it was possible a figure like al-Zawahri would be guarded by fighters of different nationalities. He also said the protected man could have been a top local tribesman.
Last year, Russian authorities revealed that al-Zawahri was detained in Dagestan in 1997 after visiting Chechnya under an assumed name and held in a pretrial detention center for a few months. He was released and expelled from Russia after authorities failed to establish his identity.
Earlier, President Pervez Musharraf said commanders believed they had a "high-value" target surrounded. Four senior Pakistani officials then said they believed al-Zawahri was the target, based on the level of resistance and intelligence placing him in the region recently. The government has been cautious, saying it would not know who was present until the operation is completed.
Hussain said 400 to 500 militants are believed to still be fighting, using mortars, AK-47s, rockets and hand-grenades in a face-off with troops.
The military gave no updated details of casualties. On Friday, Maj. Gen. Shaukat Sultan put the number of troops killed at 17, most in a disastrous initial assault Tuesday. Pakistan says 26 militants also have been killed.
Thousands of tribal residents fled their homes, and on Saturday, a small bus packed with villagers from near Wana was hit by gunfire and rockets from a Pakistani helicopter, killing 12 people, eight of them women, and injuring seven, an intelligence official in Wana said on condition of anonymity.
Sultan confirmed the incident but blamed firing by militants. He said that seven people, including five women, were killed and 13 injured.