Turkey blamed the Syrian regime for the deaths of two of its soldiers on Thursday in the rebel stronghold of Idlib, as tensions also escalated with Moscow which accused Ankara of "supporting terrorists".
The situation in Idlib province in northwestern Syria has grown increasingly volatile in recent weeks, with a Syrian offensive triggering a humanitarian crisis as close to a million civilians flee the violence.
Turkey built 12 military observation posts in the region as part of a 2018 deal with Russia to prevent a regime onslaught, but its forces have come under increasing attack.
Turkey blamed the two deaths on Thursday on a Syrian jet.
It brings the number of Turkish personnel killed in clashes with Syrian forces this month to 16. Five others were wounded on Thursday, the defence ministry said.
Turkey's President Recep Tayyip Erdogan warned this week of an "imminent" operation against Damascus unless it pulled its forces back behind Turkish positions by the end of February.
The defence ministry said it retaliated against regime forces on Thursday, with "over 50 regime elements, five tanks, two armoured personnel carriers, two armoured pickups and one howitzer destroyed."