Islamist rebels shot down a warplane on Tuesday in an area south of the city of Aleppo where insurgents are battling the Syrian army and allied militias, the Syrian Observatory for Human Rights said.
The monitor said a plume of smoke was seen as the plane caught fire before it fell in the Talat al-Iss highland, where al Qaeda-affiliated rebels have come under heavy bombardment by Syrian and Russian planes since they captured the area this week.
Syria's military said a Syrian warplane was shot down by a surface-to-air missile in Aleppo province and that its pilot ejected, state media reported.
A monitoring group and a rebel source said the pilot was captured by the al-Qaeda-linked Nusra Front. The military source quoted by state media said the plane was on a reconnaissance mission.
Russia's Defence Ministry said on Tuesday its war planes did not carry out any tasks near the Syrian city of Aleppo on Tuesday, RIA news agency reported.
Videos downloaded on social media also showed footage of the plane and pictures of the wreckage of a burnt plane surrounded by rebels.
Aerial supremacy has been a major advantage for the Syrian army that has been battling insurgents seeking to overthrow President Bashar al-Assad.
Foreign-backed rebels have long demanded anti-aircraft weapons to offset the impact of devastating aerial raids by Syrian forces and since September Russian planes, but their backers have been wary of delivering weapons that could fall into the hands of hardline groups.
A fragile "cessation of hostilities" truce has held in Syria for over a month as the various parties try to negotiate an end to the five-year-old civil war.
But the truce excludes Islamic State and Nusra Front, and air and land attacks by Syrian and allied forces continue in parts of Syria where the government says the groups are present.
