The number of terrorists linked to the PKK and its Syrian wing the YPG eliminated has reached 21 following the group’s "treacherous attack" on the Karkamış district and Köprübatı border post of Gaziantep province, Turkey's Defense Ministry announced Thursday.

The terrorists were killed in retaliatory strikes in "self-defense" in the Ain al-Arab district of northern Syria, it said in a statement.

The army continues targeting the YPG/PKK terrorist organization, the statement added.

The ministry also said one Turkish soldier was killed in the YPG/PKK terrorist group's mortar attacks targeting Karkamış and the Köprübatı Border Post. Earlier, the ministry said four Turkish soldiers and one civilian were injured in the terrorist group's attacks from northern Syria's Ain al-Arab.

Such incidents of cross-border fire have occurred sporadically in past years during the war in Syria.

Since 2016, Turkey has launched a trio of successful counterterrorism operations across its border in northern Syria to prevent the formation of a terror corridor and enable the peaceful settlement of residents – namely, the Euphrates Shield (2016), Olive Branch (2018) and Peace Spring (2019) operations.

In its more than 40-year terror campaign against Turkey, the PKK – listed as a terrorist organization by Turkey, the United States and the European Union – has been responsible for the deaths of over 40,000 people, including women, children and infants.