Turkish forces neutralised YPG members after they had attacked Turkey-backed FSA forces in northern Syria, the Turkish military said on Wednesday.
Turkey's army said YPG militants opened fire on Free Syrian Army (FSA) forces in the Maranaz area south of the town of Azaz in the north of the country.
"Fire support vehicles in the region were used to retaliate in kind against the harassing fire and the identified targets were destroyed," the Turkish military said.
TRT World's Alican Ayanlar has more from Gaziantep on Turkey's border with Syria.
Ankara was angered by a US decision last month to arm the YPG as part of the battle to dislodge Daesh from its de facto Syrian capital Raqqa, due to the YPG's links with the PKK, which is listed as a terrorist organisation by Turkey, the US and the EU.
Faced with turmoil across its southern border, Turkey sent troops into Syria last year to support FSA forces fighting both Daesh and the YPG which controls a large part of Syria's northern border region.
President Recep Tayyip Erdogan has said Turkey will not hesitate to take tougher action against the YPG in Syria if Turkey believed it is necessary.
US-backed YPG recruits children despite pledge
In its annual report on trafficking persons released on Tuesday, the US State Department stated that the YPG recruits child soldiers, both boys and girls, as young as 12 years old, despite a pledge to stop the practice.
"As reported by an international organisation in June 2015, the recruitment and use of children in combat in Syria has become “commonplace”, and documented cases of child soldiers continued to increase in 2016. Syrian government forces, pro-regime militias, and armed groups, including the Free Syrian Army (FSA) and FSA-affiliated groups, Kurdish forces [YPG], ISIS [Daesh], and Jabhat al-Nusra – the al-Qa’ida [al Qaeda] affiliate in Syria – continue to recruit and use boys and girls as soldiers, human shields, suicide bombers, and executioners, as well as in support roles."
Three years ago the YPG promised to stop using child soldiers. But the US report indicates this has not happened, regardless of continued US-backing of the group.
"Despite having signed a pledge of commitment with an international organisation in June 2014 to demobilise all fighters younger than 18 years old, the Kurdish People’s Protection Units (YPG) recruited and trained children as young as 12 years old in 2016," the report stated.