Pakistani soldiers killed at least eight advancing Taliban fighters as they waged a major offensive against militants along the Afghan border Monday, intelligence officials said, while a top U.S. senator and general met with officials in the nuclear-armed nation.

Both the Pakistani army and the Taliban have claimed early victories in the clashes in South Waziristan, a tribal region that Al Qaeda and other Islamist extremists use as a base to plot attacks on the Pakistani state, Western troops in Afghanistan and civilian targets throughout the world. The U.S. has backed the military offensive in the remote, rugged area.

The army said Sunday that 60 militants and six soldiers have been killed since the offensive began Saturday. Two intelligence officials said at least eight more militants died Monday in a fierce battle in the Khaisur area, where they were coming closer to troop positions.

The officials spoke on condition of anonymity because they were not authorized to divulge the information to media on the record. They did not speak of any military casualties.

The Taliban claimed Sunday to have inflicted "heavy casualties" and pushed advancing soldiers back into their bases. It is nearly impossible to independently verify any of the claims because the army is blocking access to the battlefield and surrounding towns.

The military offensive is focused on eliminating Pakistani Taliban militants linked to the Mehsud tribe, who control roughly 1,275 square miles of territory, or about half of South Waziristan. Part of the strategy involves striking deals with other militant groups and tribes in the region.

Some 10,000 Pakistani militants and about 1,500 foreign fighters are believed to operate in the region, though many are likely to avoid conventional battles in favor of guerrilla attacks.

Accounts from residents and those fleeing Sunday suggested that the some 30,000 troops pushing through South Waziristan from three directions face tougher resistance than in the Swat Valley, another northwest region where insurgents were overpowered earlier this year.

The army has been relying heavily on airstrikes and artillery against militants occupying high ground. Officials have said they envisage the operation will last two months, when winter weather will make fighting difficult.

As many as 150,000 civilians -- possibly more -- have left in recent months after the army made clear it was planning an assault, but some 350,000 people may be left in the region.

The U.S. has rushed to send equipment, such as night-vision goggles, to aid the offensive.

U.S. Central Command chief David Petraeus, who oversees the wars in Iraq and Afghanistan, was in Pakistan on Monday visiting top officials, while U.S. Sen. John Kerry also was meeting political and military leaders, the U.S. Embassy said.

Kerry in particular was expected to try to ease tensions with Islamabad and the army over a multibillion dollar U.S. aid package for the country that some here says comes with unacceptable strings attached.