Top Al Qaeda terrorists may have escaped a siege by thousands of Pakistani soldiers through several secret tunnels leading from mud fortresses to a dry mountain stream near the border with Afghanistan, a security chief said Monday.

The longest tunnel found so far was more than 1 mile long and led from the homes of two local men — Nek Mohammed and Sharif Khan — to a stream near the frontier, said Brig. Mahmood Shah, head of security for Pakistan's tribal regions.

"There is a possibility that the tunnel may have been used at the start of the operation," Shah told journalists in Peshawar (search), the provincial capital. He said the tunnels began at the homes in the village of Kaloosha and led in the direction of a mountain range that straddles the border.

Three senior officials have told AP that they believe Al Qaeda No. 2 Ayman al-Zawahri (search) may have been at the site, though the government has repeatedly said it does not know who is inside. President Gen. Pervez Musharraf said Thursday that a "high-value" target was likely involved.

The militants may have used the tunnel to escape during the disastrous first day of the operation on Mar. 16, when at least 15 soldiers were killed in fierce fighting. Still, Lt. Gen. Safdar Hussain, the commander of the operation, said over the weekend that authorities believe an important terrorist remains inside, based on the level of resistance of the holdouts.

Pakistan's military said it was conducting DNA tests to identify six suspected foreign terrorists killed in the fighting, but would not elaborate on whether they included any important terror figure.

Five bodies of what appeared to be 25- to 30-year-old men were displayed to journalists at a military mortuary in Rawalpindi, a city near the capital Islamabad (search), late Sunday. Al-Zawahri, an Egyptian surgeon, is 52 years old.

The bodies were laid out on stretchers and in open coffins in bloodied clothes.

Military officials said they were all foreigners, but it was impossible for journalists to determine their nationality. They said the sixth body had decomposed and that it would have been inhumane to show it.

"At this moment, whatever information we have about the tests we would not like to give out until we are 200 percent sure who they are," army spokesman Maj. Gen. Shaukat Sultan told a press conference.

"For us, every foreigner who is caught or killed, is important because we do not know who they are," Sultan told AP earlier. "We took the decision to do DNA tests to confirm the identities of these people."

"I cannot say if any among them is al-Zawahri," he said.

In Wana on Monday, an 18-member tribal peace delegation crossed through a tight military cordon for talks with elders of the Yargul Khel tribe, believed to be fighting alongside the Al Qaeda militants.

The delegation, carrying a white flag, was bringing three government demands: that the fighters free 12 soldiers and two government officials taken captive last week; that they hand over tribesmen involved in the fighting; and that they kick out any foreigners or show the military where to track them down.

Shah said that "in light of the past experience we are not very hopeful" the delegation would succeed.

Also Monday, Gen. John Abizaid, leader of the U.S. Central Command, was in Pakistan on an unannounced visit, Sultan said. He said a top army official met with Abizaid — who oversees U.S. forces in Afghanistan and Iraq — and insisted the trip had nothing to do with the offensive in Wana.

Some 5,000-6,000 Pakistani forces have been fighting 400-500 foreign militants and tribesmen holding out in fortress-like compounds under siege in Pakistan's largest military operation in its tribal regions near Afghanistan since the government threw its support behind the U.S.-led war on terrorism in late 2001.

A provincial government official told AP that several vehicles carrying soldiers were hit by rocket fire at Jandola village, 30 miles east of Wana on Monday. It was not immediately clear whether any soldiers were killed or wounded, or who the attackers were.

"We only know that some army vehicles, which were going to Wana, have been hit," said the official, who spoke on condition of anonymity. Pakistani military officials could not be immediately reached for comment.

Shah said 123 suspects have been arrested in the week-old offensive. He said the homes of 13 tribesmen accused of harboring the terrorists were leveled on Sunday and Monday.

Shahzad Uddin, a resident in Wana, the main town in South Waziristan, reported fighting resumed between army troops and militants for three hours before dawn in Duz Ghondai, a village about 5 miles to the west, the scene of earlier battles.

Shah said there had been no fire since the tribal delegation arrived at around 10 a.m. Monday. But he refused to call the lull a cease-fire, and said fighting would resume if the militants refuse to surrender.

Last week the military reported at least 17 soldiers and 26 militants had died in the initial fighting, and local officials say two dozen local people died in shooting over the weekend.

In Afghanistan, U.S. Ambassador Zalmay Khalilzad told the AP on Sunday that the United States was "very encouraged" by the ongoing Pakistani offensive. He said senior Taliban and Al Qaeda leaders were plotting attacks on Afghan and U.S. targets from Pakistan.

"We know several key Taliban figures are there, and there is some sense that some of the remaining Al Qaeda leaders are in the border area on the other side," Khalilzad said.

Shah reiterated a pledge not to turn any captured Pakistanis over to a foreign country, presumably the United States. That promise did not apply to the foreign militants.

Security officials said their prisoners included Pakistanis, Arabs, Chechens, Uzbeks and ethnic Uighurs from China's predominantly Muslim Xinjiang province. They added it is difficult to distinguish the foreigners from locals, as they have often lived in the region for a long time and speak the local Pashto language.

The operation has forced thousands of villagers from their homes, and provoked deep anger at the army. According to local government officials and intelligence officers, about two dozen local people were killed in attacks on five vehicles Saturday.

In the neighboring tribal region of North Waziristan, attackers fired four rockets at a paramilitary training school near the town of Miran Shah on Sunday night, wounding one soldier, a government official there said on the condition of anonymity.