Troops demolished homes Friday of tribesmen accused of sheltering Al Qaeda (search) fighters, while the government said it would reserve judgment on a tape purportedly of the No. 2 figure in the terror group calling for the overthrow of President Gen. Pervez Musharraf (search).

Pakistan's military has now demolished about 40 to 50 of the mud-brick, fortress-like homes of tribesmen on the border of Afghanistan who are accused of proving protection to foreign Al Qaeda fighters, officials said on condition of anonymity.

Interior Minister Faisal Saleh Hayyat told lawmakers on Thursday that more than 20 terrorists were confirmed killed and that he expected 30 to 35 more bodies of terrorists would be recovered as the operation concludes.

Meanwhile, Pakistan's government reserved comment Friday on the latest purported tape of by Al Qaeda's second-in-command, Ayman al-Zawahiri (search). The message called Musharraf a traitor and urged people to overthrow his government.

Information Minister Sheikh Rashid Ahmed said the government would only comment after the authenticity of the tape was established. It was aired on the Arabic satellite channel Al-Jazeera late Thursday. The speaker on the tape sounded like al-Zawahiri and made references to the Islamic holy book, the Quran, which is known to be al-Zawahiri's style.

The tape was released as Pakistan pressed on with its biggest counterterrorism operation since Musharraf threw his support behind the U.S.-led war on terrorism in late 2001.

Last week, Musharraf said a "high-value" terrorist suspect could be hiding in tribal South Waziristan, where hundreds of militants have battled thousands of Pakistani forces. The government did not identify the suspect, but a number of senior officials privately said they believed it could be al-Zawahiri.

The discovery of a one-mile tunnel between mud fortresses where militants were hiding has fueled speculation that any high-value target may have escaped in the March 16 initial assault, when paramilitary forces were surprised by the intensity of resistance and suffered heavy casualties.

It was not known when the purported al-Zawahiri tape was made, but the speaker could be referring to South Waziristan when he says Musharraf has put the army in a "miserable state."

"Musharraf ruins your natural fences — those tribes on the border — by engaging you in a fight with them," the speaker said.

Officials said Thursday that Pakistani forces have killed more than 50 alleged terrorists and captured 163 in the operation although they did not identify them.

The military has refused to give details of troop casualties, although officials have reported at least 30 Pakistani army and paramilitary troops have been killed and a dozen more held captive.

Officials in Wana, the main town in South Waziristan, said that in recent days fierce fighting involving artillery and helicopter gunships has subsided as the remaining militants have scattered into small groups.

Throughout the week, tribal elders have been shuttling in and out of the battle zone, just outside Wana, to persuade the local Yargul Khel tribe to hand over foreign terrorist suspects and free 12 paramilitary troops and two government officials taken hostage.

Musharraf, who took power in a bloodless 1999 coup, is facing rising political opposition to the Wana operation, which reflects widespread anger in this conservative region about the military deployment and growing unease across Pakistan about his support for the U.S.-led war on terror.