The situation in Idlib province in northwestern Syria has grown increasingly volatile in recent weeks, with a Syrian offensive triggering a humanitarian crisis as close to a million civilians fled the violence.
Last year, Turkey had killed 28 Kurdish militants in retaliation to an attack which left three Turkish soldiers dead.
The PKK, regarded as a terrorist group by Turkey, the US and the EU, has waged an insurgency against the Turkish state since 1984.
Turkey has retaliated against the attacks under the rules of engagement and its right to legitimate self-defence, killing nearly 200 Assad military personnel since last week.
Idlib has been a stronghold of the opposition and anti-government armed groups since the outbreak of the Syrian civil war in 2011.
In September 2018, Ankara and Moscow reached an agreement in Sochi, Russia, to turn Idlib into a de-escalation zone in which acts of aggression are expressly prohibited.
Turkey launched a cross-border assault on Kurdish fighters after the US decided to withdraw troops from Syria, a move that was criticised by the Republicans, with some terming it a “betrayal” of the Kurds.
