However, there was no official word yet on the new offensive.

The military backed by helicopter gunships launched a major offensive after militants fired rockets at the military positions last night in Wana, the headquarters of South Waziristan, reports quoting witnesses said, adding they heard the helicopters fire rockets at suspected militant hideouts.

Today's offensive coincides with the visit of US Deputy Secretary Richard Armitage, who arrived here last night, to hold talks with President Pervez Musharraf and other leaders.

The army has been trying to persuade tribesmen protecting several hundred suspected foreign militants to hand them over for registration.

Instead, the militants -- who accuse the security forces of fighting on behalf of the Americans who are continuing to mount anti-Taleban operations across the rugged border in Afghanistan -- have been digging in, staging lightning strikes against the military.

Earlier, Musharraf had said between 500-600 al-Qaeda militants were hiding in the South Waziristan semi-autonomous area. He has repeatedly pledged not to allow foreign militants to be based in his country.

More reports from Pakistan