The Syrian Kurdish YPG militia said that Saturday's Turkish air strikes on Syria's Afrin region left it with no choice but to fight back, saying Ankara had hit civilian neighbourhoods.
"We will defeat this aggression, like we have defeated other such assaults against our villages and cities," the YPG, which has battled Islamic State with U.S. backing, said.
The YPG urged men and women in north Syria to join its ranks to protect Afrin.
Turkey opened a new front in Syria's war on Saturday, striking the Afrin region and raising the prospect of deeper strains between Ankara and NATO ally Washington.
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