BRUSSELS (AP) — Ambassadors from the NATO military alliance are holding emergency talks Friday at the request of Turkey following the killing of 33 Turkish soldiers in northeast Syria,

NATO Secretary-General Jens Stoltenberg said in a statement that the talks Friday morning would be held under Article 4 of NATO’s founding treaty, which allows any ally to request consultations if it feels its territorial integrity, political independence or security is threatened.

The air strike by Syrian government forces that killed the Turkish soldiers in northeast Syria marks the largest death toll for Turkey in a single day since it first intervened in Syria in 2016.

The deaths were a serious escalation in the direct conflict between Turkish and Russia-backed Syrian forces that has been waged since early February.

At least 54 have now been killed in Idlib since the start of February.