Pakistan Qaeda Standoff Continues

Thousands of Pakistani army reinforcements joined a round-the-clock offensive Friday in lawless border villages where al Qaeda's No. 2 leader was believed to be surrounded along with hundreds of other militants hunkered down in heavily armed mud fortresses.

The troops set up a cordon around a 20-square-mile area, as residents — many said to be sympathetic to the militants — streamed out of the besieged region in pickup trucks loaded with their families and possessions. Afghan authorities reported the arrests of midlevel terrorist leaders on their side of the border.

Army spokesman Gen. Shaukat Sultan said the army believes a mix of foreigners and local Pakistani tribesmen are holed up in several villages in South Waziristan, where Pakistani paramilitary forces began an operation against al Qaeda and Taliban fugitives four days ago.

"From the type of resistance we are getting … the militants could be anything from 300 to 400," he told a news conference.

Sultan said authorities' intelligence assessment was that a high-level fugitive was among the fighters, although he had not been seen and it was unclear whether it was

"The type of resistance, the type of preparation of their defensive positions, the hardened fortresses they have made means we can assume that there could probably be some high-value target there," Sultan said from the army press office in Rawalpindi, a city near the capital, Islamabad.

However, CBS News Correspondent Lara Logan reports some observers say the

Sultan disputed claims by four senior Pakistani officials that captured militants had revealed that al-Zawahri was among them, and possibly injured.

"So far, whatever people we have apprehended, we have not got confirmation from them," he said — but quickly added the army could not share such intelligence anyway in an ongoing operation.

Villagers in Wana, the main town in South Waziristan, said

Helicopter gunships fired rockets at houses in Shin Warsak, five miles southwest of Wana, the villagers said. Residents reported seeing scores of army trucks carrying troops and weapons moving from Wana to the targeted areas.

Pakistani President Gen. Pervez Musharraf also said Thursday a "high-value" target was believed trapped. The four senior Pakistani officials told The Associated Press on condition of anonymity that intelligence indicated it was al-Zawahri.

But the White House was taking a very cautious approach to the reports.

"There clearly is a fierce battle going on there on the Pakistani-Afghan border," national security adviser

Pakistani Interior Minister Faisal Saleh Hayyat told AP that authorities hoped to wrap up the raid "during the next 48 hours."

Across the border in Afghanistan, U.S. troops stand ready to back Pakistan's army if needed, but they have their own battles to fight with al Qaeda, reports CBS News Correspondent Chris Lawrence.

Lt. Colonel Bryan Hilferty described their mission as, "stripping away what little support they may have had among the population."

Elsewhere Friday, U.S. and Afghan troops called in air power to attack insurgents who killed two American soldiers in a gunbattle in central Afghanistan, the military said.

On Thursday, two American soldiers were killed and two wounded when they were attacked by militia in a village near Tarin Kowt, some 250 miles southwest of the capital Kabul. The military said the American soldiers returned fire, killing at least five and wounding an undetermined number of others.

The United States has offered a $25 million reward for information leading to al-Zawahri's capture. On Thursday, the U.S. House of Representatives doubled the reward for bin Laden's capture to $50 million.

Al-Zawahri, a 52-year-old former Egyptian surgeon, is believed to be the brains behind the terror network, with bin Laden serving more as spiritual leader and financial backer. He is also thought to have served as the al Qaeda leader's personal physician.

Often seen by bin Laden's side in videos released to Arab television networks, the doctor was also thought to serve as al Qaeda leader's personal physician.

Al-Zawahri's Egyptian Islamic Jihad was believed behind the assassination of President Anwar Sadat during a Cairo military parade in 1981. He merged the organization with al Qaeda in 1998.

"Al Qaeda is not just one man," Rice told the Early Show "It's a network. Obviously, when you can kill or capture one of the major leaders — and Zawahri is clearly one of the major leaders — it would be a boost to the war on terrorism. But I don't think we should jump to the conclusion it would by any means disable al Qaeda.