Pakistani forces have pressed on with their attacks as they move to drive out the Taliban from its bases in a lawless region on the Afghan border.

Taliban fighters offered fierce resistance as ground troops backed by warplanes and artillery pushed into South Waziristan, the mountain headquarters of the notorious Tehrik-i-Taliban Pakistan (TTP). Pakistan said it killed more than 60 militants and lost 11 soldiers as a force of 30,000 pushed into Taliban's tribal stronghold.

Intelligence officials said at least eight more militants have died in a fierce battle in the Khaisur area, where they approached troop positions.

"There has been artillery fire throughout the night. It was very heavy firing," Noor Wali, a resident of Wana, the main town in the region, said by telephone. Officials have said they think the operation will last two months, when winter weather will make fighting difficult.

America has rushed to send equipment such as night-vision goggles to aid the offensive. General David Petraeus, the head of US central command, who oversees the wars in Iraq and Afghanistan, was in Pakistan visiting top officials, while the US senator John Kerry was meeting political and military leaders.

Militants detonated roadside bombs and opened fire on helicopter gunships. Villagers, some of them women, waved white flags and troops searching houses discovered large weapons caches, the military said. As many as 150,000 civilians, possibly more, have left in recent months after the army made clear it was planning an assault. About 350,000 people may be left in the region.

In a statement, the military said tactical heights near Razmak, a mountain village at the northern edge of South Waziristan, had been captured following fighting that killed 10 militants and two soldiers.

The Taliban denied the army claims and a spokesman insisted the guerrillas had inflicted "heavy casualties" that forced the invading soldiers back into their bases. "We know how to fight this war and defeat the enemy with the minimum loss of our men," Azam Tariq told the Associated Press from an undisclosed location.

The conflicting versions were impossible to reconcile. Inaccessible at the best of times, much of South Waziristan has been sealed off since the operation started on Saturday morning. Phone connections to Waziristan and nearby areas have been disconnected.

The officials said the fighting was concentrated around the town of Shakai, where soldiers are pushing in from the south-west.

"The militants are putting up stiff resistance at the Shakai front," said an intelligence official in the region.

There was less fighting on another front in the Spinkai Raghzai area, where soldiers were moving in from the south-east, said the unidentified official.

The fight – pitting 30,000 soldiers against 10,000 Taliban and al-Qaida militants, according to the army – followed two weeks of audacious assaults in cities that left more than 175 people dead and underlined the militant threat to national stability.

In the most shocking incident, a team of 10 gunmen laid siege to the army headquarters in Rawalpindi for 22 hours. All but one of the attackers were killed. The army said the raid was orchestrated from South Waziristan.

The army has surrounded a mountainous swath of South Waziristan that is controlled by the Mehsud tribe, whose most notorious member, Baitullah Mehsud, was killed by a US drone in August. Mehsud's successor as leader, Hakimullah Mehsud, vowed to take revenge, apparently triggering the recent wave of militant attacks.

Soldiers are attacking the Mehsud territory from Razmak in the north, Jandola in the east and Wana in the south. Officials estimate the drive will take a minimum of six weeks and could stretch through the winter. The non-Mehsud parts of South Waziristan, which are controlled by the rival Wazir tribe and border with Afghanistan, have not been affected.

The army hopes to repeat the success of its campaign against the Taliban in Swat this summer. But few doubt this operation will be harder, longer and with a greater risk of failure.