Pakistani troops have reportedly surrounded a key stronghold of Uzbek fighters in South Waziristan.
Military officials say the town of Kaniguram is also the "operational centre" for the Taliban in Pakistan.
South Waziristan is considered to be their main sanctuary outside Afghanistan.
Pakistan launched an offensive in South Waziristan after a wave of attacks, believed to have been orchestrated from there, killed more than 150 people in October.
The BBC reports the army says the offensive is "making good progress".
The army has declared South Waziristan a closed military zone until the operation ends.
Thousands of civilians have fled the conflict zone since hostilities broke out.
Kaniguram has between 85,000-90,000 residents. It is surrounded by mountains, with roads connecting it to the rest of the region generally blocked in winter.