Turkish citizens can rest assured that the Turkish military will hold the Assad regime accountable for its attack on their soldiers in Idlib, Presidential Spokesperson İbrahim Kalın said Friday.

The airstrike by Syrian regime forces that killed 33 Turkish soldiers in northwestern Idlib province marks the largest death toll for Turkey in a single day since it first intervened in Syria in 2016.

Backed by heavy Russian airstrikes, Syrian regime forces have been fighting since the start of the year to recapture the Aleppo countryside and parts of neighboring Idlib, the last opposition stronghold in the country. The advances have sent hundreds of thousands of Syrian civilians fleeing toward the border with Turkey in the biggest single displacement of the nine-year war.

It has also upset the fragile cooperation between Ankara and Moscow, which back opposing sides in the conflict.