Islamabad, Pakistan (CNN) -- A deadly clash between government forces and Taliban militants erupted in Pakistan's restive tribal belt Tuesday, marking continued unrest in the Orakzai district -- an area government officials last year claimed they had largely pacified.
Pakistani Army Col. Asif Khan said 35 militants and two security force members were killed as a result of the fighting in the district, located west of the provincial capital of Peshawar.
Sixteen other security personnel were injured, he said.
A second Pakistani official estimated lower numbers of militants killed, putting the death toll at 20, while saying 21 service members had been injured.
The clash occurred after Pakistani security forces raided a militant hideout in the ethnic Pashtun-dominated area, the official said, who declined to be named because he is not authorized to speak with the media.
A spokesman for the Tehrik-e-Taliban Pakistan, an umbrella militant group that operates in the region, said the group took responsibility for the attack, claiming it was in retaliation for an earlier government operation.
Ehsanullah Ehsan, the Pakistani Taliban spokesman, said five soldiers were killed during the clashes.
He denied that any militants died in the attacks, but said 15 were injured.
In 2011, the government announced that it had largely cleared the area of militants following a major military operation. But officials recently acknowledged that the Taliban actually still maintains pockets of control.
Militants are believed to have found sanctuary in Orakzai after being routed in government military operations in South Waziristan -- a volatile mountainous region that borders Afghanistan.
Hakimullah Mehsud, who assumed leadership of the Pakistani Taliban in 2009, is also believed to have supporters in Orakzai, stemming from when he worked as a militant commander in the area.
Mehsud got Washington's attention after he claimed responsibility for organizing a deadly suicide attack against a CIA base in southern Afghanistan in December 2009.
The region has long been considered a staging ground for Taliban attacks against Pakistani security forces as well as NATO and Afghan troops in southern and eastern Afghanistan.
CNN's Reza Sayah and Aliza Kassim contributed to this report