A total of 21 PKK terrorists were killed in an anti-terror operation carried out Monday and Tuesday in the rural areas of southeastern and eastern Turkey and northern Iraq, the Turkish Armed Forces (TSK) said Tuesday in a written statement.

Four PKK terrorists were killed in airstrikes carried out Tuesday in the rural areas of eastern Van province, while five other terrorists were killed in air-supported counter terrorism operations in northern Iraq's Hakurk region, the TSK statement said.

The TSK also carried out an anti-terror operation in northern Iraq's Zap region, targeting large shelters and logistic centers used by the terrorist organization, during which 11 PKK terrorists were killed.

Another PKK terrorist was killed in the air-supported operation in southeastern Siirt's Pervari region, which was launched Monday evening upon receiving intelligence. The airstrikes destroyed 10 shelters and one supply point used by the terrorist group, the statement continued.

Meanwhile, four PKK terrorists who were fleeing from the group willingly surrendered Sunday to Turkish forces, another statement by the TSK said Wednesday.

Two male terrorists fled from the inhumane conditions at the PKK's Hakurk camp and surrendered in the rural areas of southeastern Hakkari's Şemdinli district, while two female terrorists surrendered to Turkish soldiers at the Gedik Hill also in Şendinli, the statement added.

Meanwhile, 837 terrorists killed since the start of the year, and the majority -- 431 -- were killed in Turkey, the military said in a statement.

The remaining 406 were killed outside Turkey's borders, most of them likely casualties in Operation Euphrates Shield in Syria, which ended March 29.

The military said it had captured 82 terrorists inside Turkey. In addition, it said 157 PKK terrorists surrendered.

These operations led to the capture of weaponry including 61 machine guns, 38 sniper rifles, 122 grenade launchers and anti-tank weapons as well as more than 500,000 rounds of ammunition.

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.

Since that time, the PKK has 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.