Turkey's Defence Ministry said on Tuesday that it would retaliate "in the strongest way, without hesitation" against any attack on its observation posts in Syria's northwestern Idlib province by Bashar al-Assad's forces.
"The regime's attacks on Idlib are massacring innocent civilians and causing humanitarian tragedy," the Turkish defence ministry said on Twitter.
"A response will be given in self-defence to any attempts that would jeopardise the security of our observation and control posts in the region," the ministry added.
Ankara established 12 observation posts under a September 2018 deal with Russia, a major ally of Syrian President Bashar al-Assad, to prevent any onslaught in Idlib.
The city is home to some three million people, around half of whom have been displaced by violence in other areas.
Regime forces entered a town south of Idlib city on Tuesday, in a significant advance for Assad as he seeks to recapture rebel-held territory in the country's northwest, a war monitor and pro-Assad media said.
Despite a ceasefire arranged by Russia and Turkey, the regime's deadly offensive has sparked an exodus of thousands of civilians toward the Turkish border.
