ANKARA, Turkey (AP) — Nine Turkish soldiers were killed in an air strike in northeast Syria late Thursday, a Turkish official said.

Hatay Governor Rahmi Dogan said other soldiers were severely wounded in the attack by Syrian government forces and were being treated at hospitals in Turkey. Hatay borders the Syrian province of Idlib.

Turkish President Recep Tayyip Erdogan called an emergency security meeting in Ankara, broadcaster NTV reported. Foreign Minister Mevlut Cavusoglu spoke to NATO Secretary General Jens Stoltenberg by telephone, according to state-run Anadolu news agency.

The deaths are the largest number of fatalities suffered by Turkish forces in a single day since Ankara started sending thousands of troops into Idlib in recent weeks in a bid to halt an advance by Syrian forces that has sent hundreds of thousands of displaced people towards the Turkish border.