Rebel fighters shot down Russian plane over Syria's Idlib province on Saturday, a monitor said, taking its Russian pilot captive.
However, later reports suggested the Russian pilot had been killed by rebel fighters after he resisted capture by opening fire with his pistol.
The Britain-based Syrian Observatory for Human Rights says the warplane was downed Saturday afternoon near the rebel-held town of Saraqeb, which Syrian troops have been trying to reach under the cover of Russian airstrikes.
No group immediately claimed responsibility for the attack but hardline opposition groups and the jihadist Hayat Tahrir al-Sham (HTS) are active in Idlib.
The incident comes as Syrian government forces, backed by Russian air support and Iranian arms, have intensified their offensive into Idlib.More news: French President Emmanuel Macron poses with Rihanna
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Idlib has been a haven for tens of thousands of rebels and civilians who were forced to abandon their homes in other parts of western Syria that the government and its foreign military allies have recaptured from terrorists.
"We believe two Russian planes struck the convoy of civilians on the highway and left at least seven killed and twelve injured, mostly elderly and children", said Ammar al Adnan, a civil defence worker from Saraqeb.
Russian Federation is a key ally of President Bashar al-Assad, and has been waging a military campaign on behalf of his forces since 2015. According to several Syrian reports, the pilot was captured by a local terrorist group whose members then executed him, though this has not been officially confirmed. The UN said some 100,000 civilians have been displaced. One of the soldiers was killed when a Turkish tank was hit in Afrin.
It is not clear which group was responsible for downing the fighter jet.
Turkey shares a 911-kilometre border with Syria.