More than 120 people were killed in a 12-day offensive in the South Waziristan tribal region that ended on Sunday and one intelligence official said a sweep of North Waziristan was now being considered.

About 3,500 fresh troops had been sent to reinforce more than 13,000 military and paramilitary troops already deployed in the rugged region, the official said.

"The fresh troops reached South Waziristan on Thursday," he said.

Pakistan has mounted its biggest campaign to pacify the lawless and largely autonomous tribal region on the Afghan border and clear the area of foreign fighters.

The offensive follows two assassination attempts on President Pervez Musharraf in December that he linked to militants hiding in the tribal area.

As Pakistani forces hunt on their side of the border, US forces have mounted an operation on the Afghan side in what the Pentagon has called a "hammer and anvil" action to catch al-Qaeda leaders, possibly including Osama bin Laden.

Pakistani leaders say they have no idea where bin Laden and other al-Qaeda leaders are, but several hundred al-Qaeda fighters, believed to include Arabs, Afghans, Uzbeks and Chechens, are believed to have escaped the recent fighting.

Government representatives told tribal elders at a meeting in the South Waziristan town of Wana that a group of five Pakistani tribal fighters, wanted by the authorities for giving refuge to foreign militants, had to surrender.