PESHAWAR, Pakistan – Four days of fierce fighting in northwestern Pakistan left 30 soldiers and nearly 100 militants dead as the army attempted to wrest control of a remote, mountainous valley from the Taliban and their allies, military officials said Monday.

The army launched its offensive in the Tirah Valley on Friday after weeks of fighting between rival militant groups forced tens of thousands of civilians to flee the area. The valley is located in Khyber, part of the semiautonomous tribal region bordering Afghanistan, the main sanctuary for the Taliban in the country.

The army has launched scores of operations against the Pakistani Taliban in the tribal region in recent years, but certain areas like Tirah have remained outside their control.

The Pakistani Taliban have been waging a bloody insurgency against the government because of its alliance with the U.S. in fighting Islamic militants, and to establish Islamic law in the country.

The fighting in Tirah over the past four days has killed 30 soldiers and 97 militants, military officials said, speaking on condition of anonymity. The air force has also conducted heavy bombing during the offensive, they said.

The officials claimed that the army has successfully seized control of a large portion of the valley from the Pakistani Taliban and their ally, Lashkar-e-Islam. The claims could not be independently verified.

More than 40,000 people have been displaced from the valley since mid-March, according to a recent report by the U.N.’s humanitarian arm.