The Syrian Observatory for Human Rights (SOHR) says 19 Syrian soldiers have been killed, following a Turkish drone strike on the province of Idlib.
The UK-based monitor says yesterday’s attacks targeted a military convoy and an army base, whilst Turkey also shot down two Syrian aircraft - after the downing of at least one of its drones.
Both pilots are understood to have parachuted to safety above the hostile province, as Syrian state news announced airspace closures in the northwest – threatening to down any encroaching aircraft.
SOHR says that regime forces were killed after Turkey targeted their positions in Jabal al-Zawiya and Al-Hamidia camp in Idlib countryside.
Turkey, which backs rebels opposing the government forces in Idlib, said it also targeted Syrian air defence systems and dozens of tanks.
The latest episodes of violence in the area follows a Syrian strike last week, which killed 33 Turkish soldiers.
NATO's ruling council held urgent talks on the crisis after the attack, Turkey calling state ambassadors together over perceived threat to territorial integrity, political independence or security.
Secretary General of the military alliance, Jens Stoltenberg, condemned "indiscriminate" attacks, during a phone conversation with Turkish Foreign Minister Mevlut Cavusoglu shortly after.
Meanwhile on Sunday, thousands of migrants and refugees massed at Turkey’s western frontier, trying to enter Greece by land and sea after Turkey said its borders were open to those hoping to head to Europe.
Turkey hosts some 3.6 million Syrians fleeing the conflict, under a 2016 deal with the European Union.
Turkey has insisted it does not want to spark a conflict Russia, a key military ally to Syria understood to have have been behind many of the attacks on government opposition.
Apart from providing some aerial surveillance, NATO plays no direct role in Syria, though its members are divided over Turkey's actions there.
Cover image: Smoke from an airstrike, allegedly carried out by Russian and Syrian forces warplanes in the town of Sarmin, northern of the rebel-held Idlib province (Picture: PA).