In an apparent move to divert army's attention from Waziristan, the militants have also stepped up attacks elsewhere in the volatile northwest, officials said.
Government forces on Tuesday killed six Taliban in Mohmand, a distant tribal region northeast of Waziristan, after militants attacked a security post and killed two soldiers. In neighbouring Bajaur, the militants shot dead the head of a pro-government tribal militia.
A senior government official in the town of Tank, the gateway to South Waziristan, told Reuters that militants had begun fleeing to neighbouring regions, a claim backed up by ordinary residents.
"I saw Uzbeks and Pakistani militants in Mir Ali as well as on my way," a tribesman, Majeed Mehsud, told Reuters.
The military says 239 militants and 33 soldiers have been killed since the offensive started on Oct. 17, but there has been no independent confirmation as foreign journalists are not allowed anywhere near the battle zone and it is dangerous even for Pakistani reporters to visit.
The offensive is a test of the government's determination to tackle Islamist fundamentalists, and the campaign is being closely followed by the United States and other powers embroiled in Afghanistan's growing conflict.
About 28,000 soldiers are battling an estimated 10,000 hard-core Taliban, including about 1,000 tough Uzbek fighters and some Arab al Qaeda members.
(Additional reporting by Izaz Mohmand, Alamgir Bitani and Mian Saeed-ur- Rehman; Editing by David Fox)