Turkey responded to a terrorist attack from Syria's northern city of Tal Rifat on Turkish soldiers in Afrin, the defense ministry said Friday.
The PKK's Syrian affiliate People's Protection Units (YPG) carried out the attack, the ministry said on Twitter.
No additional details were provided as to the nature of the attack.
Turkish Armed Forces (TSK) conducted two successful operations in northern Syria with the Free Syrian Army (FSA). In Operation Euphrates Shield, launched in August 2016, TSK backed-FSA captured bordering Jarablus, al-Rai and al-Bab districts from the Daesh terrorist group. Operation Olive Branch, launched in January 2018, cleared the Afrin district from the YPG.
In its more than 30-year terror campaign against Turkey, the PKK -- listed as a terrorist organization by Turkey, the U.S. and the EU -- has been responsible for the deaths of some 40,000 people, including women and children.