The Turkish Armed Forces (TSK) launched Operation Olive Branch with the Free Syrian Army (FSA) on January 20 to clear Afrin of the YPG, which poses a threat to Turkey's national security.
Turkey considers Syrian Kurdish fighters to be "terrorists" linked to a Kurdish insurgency inside its own borders.
Turkey has been invading Afrin, a Kurdish territory, for over month now, and has promised to extend the war into nearby Manbij, a city captured by the same Kurdish YPG forces previous year.
A Syrian convoy of humanitarian aid has reached the northern district of Afrin, which has been the target of a Turkish offensive for more than a month.
The Syrian Observatory for Human Rights says that close to 150 civilians have been killed since the start of Turkish offensive, though Turkey has disputed such claims. The Lebanon-based Al-Mayadeen TV said Turkish warplanes had killed 18 pro-government gunmen, while 19 more are missing.
Al-Mayadeen said the air strike occurred after the Popular Forces hit a Turkish helicopter gunship.
No further details were immediately available.
On Thursday, eight Turkish soldiers were martyred as a Turkish-led operation continued in the region, according to two separate statements from the Turkish General Staff.
This figure only includes Turkish soldiers, and not their Free Syrian Army auxiliaries, nor any Kurds that got killed in the fighting.
The Turkish military said on Friday at least nine terrorists were neutralised in Operation Olive Branch in Afrin, northwestern Syria. Dogan released a video from Rajo showing Turkish-backed Syrian opposition fighters firing into the distance as well as the fighters milling about.
Near the capital, Damascus, a five-hour truce went into effect on Friday, the fourth this week, with no civilians leaving the city's rebel-held suburbs known as eastern Ghouta.
Bassem Mroue is an Associated Press writer.