Units of pro-Ankara rebels known by Turkey as the Free Syrian Army (FSA) also began moving into the Afrin area of Syria which is controlled by the YPG, the state-run Anadolu news agency said.
"Our armed forces have started an air campaign in order to destroy elements" of the YPG, Prime Minister Binali Yildirim said in a televised speech.
An AFP correspondent on the Turkish side of the border saw two war planes launch air strikes inside Syrian territory, sending huge white plumes of smoke up into the early evening sky.
But these were the first reports from on the ground that the operation had begun in earnest.
A Turkish foreign ministry official said in the wake of the announcement of the air strikes that Foreign Minister Mevlut Cavusoglu held talks with US counterpart Rex Tillerson, at Washington's request.
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