Turkish war planes have bombed Syrian Kurdish militia YPG and PYD targets in Kurdish-controlled Afrin, a senior Turkish official has told Reuters.
Direct military action against territory held by Kurdish militia opens a new front in Syria's civil war and sees Ankara confronting Kurds allied to the United States at a time when Turkey's relations with Washington are reaching breaking point.
Turkey's army said earlier it had hit shelters and hideouts used by militants from three groups - the Kurdistan Workers' Party (PKK), PYD and YPG, after militants fired on Turkish positions inside Turkey.
A military statement said the operation launched on Saturday aims to protect Turkey's borders, "neutralise" Syrian Kurdish fighters in the enclave of Afrin and to save the local population from their "pressure and oppression".
The Free Syrian Army has also started to support the Turkish military in Afrin, the official said.
Turkish President Tayyip Erdogan said earlier on Saturday that a military operation in the Afrin region had begun after cross-border shelling by the Turkish army.