Pakistan is checking a tape-recording apparently by Osama bin Laden's deputy that calls for the government's overthrow, and it has vowed to step up the hunt for al-Qaeda on its Afghan border.
President Pervez Musharraf's government said more troops would be sent to its semi-autonomous tribal territories bordering eastern Afghanistan to reinforce a campaign to flush out al-Qaeda and other militants.
Pakistan officials were checking the authenticity of a defiant message purportedly sent by bin Laden's right-hand man, Mr Ayman al-Zawahri, calling on Pakistanis to overthrow Mr Musharraf and describing the Pakistani leader as a "traitor" to Islam.
Nearly 100 people have been killed since last week when paramilitary forces hunting al-Qaeda fighters and their Pakistani tribal allies were shot at as as they approached a suspect's house in the lawless South Waziristan tribal region.
The battle, involving 5,000 troops, is the biggest Pakistan has ever waged in the region, and comes after Mr Musharraf narrowly escaped two assassination attempts, blamed on Muslim militants, in December.
"There is no final confirmation, whether it's a real tape or not," Sheikh Rasheed Ahmed, Pakistan's information minister, said. "We will confirm and then we will give a reaction."
The tape, the second believed to have been made by Mr Zawahri calling for Pakistan revolt since September, came just days after Pakistan hinted its forces might have had the fugitive trapped. The military later said that was just guesswork.