Turkey opened fire on hundreds of fighters loyal to Syrian President Bashar al-Assad. The fighters arrived in the Kurdish-controlled Syrian province of Afrin on Feb. 20, news reports said, as Damascus disregarded Ankara’s warnings against coming to the aid of the Syrian Kurdish militia fighting a Turkish military assault.

The confrontation came just hours after Turkish President Recep Tayyip Erdogan said he had prevented any such incursion by Syrian government forces after speaking to Russian President Vladimir Putin and Iranian President Hassan Rouhani, Syria’s benefactors, and that Turkish troops and their allies in the Free Syrian Army (FSA) would besiege the provincial capital in a matter of days.

Later, Erdogan said that the groups, which he described as “Shiite militias in a few pickup trucks,” had acted independently and that Turkish artillery fire had repulsed the fighters. CNN Turk cited unidentified sources as saying the pro-Assad militias would not attempt such a show of force during daylight hours. Other reports could not confirm the militias had turned back.

“In my calls with Mr. Putin and Mr. Rouhani, we had already reached agreement on this," Erdogan said at a televised news conference. "Unfortunately, terrorist groups like these sometimes make missteps according to their own decisions. It is not possible for us to allow this. They will pay a heavy price for this."