Turkish security forces in the southeastern province of Diyarbakır have killed five PKK terrorists, including four of the most wanted militants, the Interior Ministry confirmed Friday.

Four of the terrorists were in the gray category of the Interior Ministry's Most Wanted list. The wanted list is divided into five color-coded categories, with red as the most wanted, followed by blue, green, orange and gray.

The terrorists were identified as: Hamit Aydoğan code-named Doctor Ferhat; Mehmet Resat Tekin code named Resit; Müslüm Irmak code named Merhas and Mesut Aktaş code named Aziz Ararat. They had a TL 300,000 each bounty on their heads.

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 PKK has since been responsible for the deaths of some 1,200 security personnel and civilians, including women and children, while more than 4,000 security personnel and over 2,000 civilians have been injured.

The terrorist organization isn't just active in Turkey but operates throughout the region, particularly in Syria and Iraq. The Turkish government has repeatedly called on the Iraqi government to eradicate the PKK threat. If not, Ankara says the Turkish military will exercise its rights and launch a cross-border operation in the area, as it did during Operation Euphrates Shield and Operation Olive Branch in Syria.