The soldiers were fighting street by street through the mountainous town of Ladha, the military said in a statement. Over the past day, the fighting has left 10 militants dead in Ladha and 30 dead across the region, it said. Eight soldiers have been injured.

In mid-October, the Pakistani government launched an offensive in South Waziristan, a semiautonomous area on the Afghan border seen as the main stronghold in the country of both the Taliban and al-Qaeda. The central government has seldom held more than symbolic control in the tribal areas, where the Taliban has operated increasingly openly in recent years.

Ladha is one of the three main Taliban strongholds in South Waziristan, according to the military. Government forces have already taken control of much of another key town, Sararogha, and are expected to launch an attack soon on Makeen, which the authorities have called the "nerve center" of the Pakistani Taliban.

"It's going fast," said army spokesman Maj. Gen. Athar Abbas, who declined to give a timeframe for when the fighting would end. "It depends — it's a lot of remote areas."

The Taliban, though, denies such claims. A Taliban spokesman told the Associated Press earlier this week that it had lost fewer than a dozen fighters, and that its withdrawals had been made strategically to pull government fighters deeper into militant territory.

Figuring out the reality is nearly impossible. The government has closed off the tribal areas to outsiders and only allows journalists into the battle zone on carefully orchestrated trips.

The offensive has drawn retaliatory militant attacks across Pakistan.

Earlier Wednesday, a group of militants ambushed a van as it traveled near Khar, the main town in the Bajur tribal region, killing two female teachers and wounding two other passengers.

Approximately 10 militants hid on both sides of a rural road and sprayed the van with automatic weapons fire as it went past, local official Adalat Khan said. The attackers then fled on motorcycles.

Pakistan's Taliban fighters are deeply opposed to modern education, particularly for girls, and have blown up schools and attacked teachers across the country.

"This is an alarming sign," said Fazal Rabi, a senior official with Bajur's tribal police force. Despite a spate of recent attacks, the government insists Bajur has been free of militants since it forced them out in an offensive earlier this year.