Turkish security forces on Thursday killed two of the most wanted PKK terrorists in a counterterrorism operation, the Interior Ministry confirmed Friday.

Celal Kaya and Haydar Gül were listed respectively in the blue and orange category of the Interior Ministry's most wanted terrorists list.

Kaya, who was in the second-highest category, had a TL 1.5-million bounty on his head, while Gul had a bounty of TL 600,000 on his.

The most wanted list is divided into five color-coded categories, with red at the top, followed by blue, green, orange and gray.

On Thursday, six PKK terrorists were killed in eastern Turkey's Tunceli province, when Gendarmerie forces clashed with the group that was preparing for an attack in rural areas, the statement said.

"In this operation, two heroic gendarmes were slightly injured and received first aid," it added.

Operations in the area continue, the provincial governor's office said.

Founded in 1978, the PKK has waged a decades-long bloody campaign against Turkey.

The PKK, which is listed as a terrorist organization by Turkey, the U.S., and the EU, resumed its armed campaign in July 2015 after a brief reconciliation period.

The group has since been responsible for the deaths of some 1,200 security personnel and civilians, including women and children. More than 4,000 security personnel and over 2,000 civilians have also been injured in PKK attacks during this period.

Turkish security forces regularly conduct counterterrorism operations in the eastern and southeastern provinces of Turkey where the PKK has attempted to establish a strong presence and bases.

Meanwhile, a Turkish soldier was killed and another injured on Friday in a PKK terror attack in eastern Turkey, according to security sources.

The terrorists used an improvised explosive device (IED) to carry out the attack early morning in eastern Iğdır province, said the sources, speaking on condition of anonymity due to restrictions on speaking to the media.

An attack in the Dilucu area also wounded another soldier.