Turkish media reports said Tuesday that Turkish jets shot down a warplane that violated national airspace at the border with Syria.
Turkish presidential sources said the downed jet was a Russian-made Sukhoi Su-24.
The Russian Defense Ministry issued a statement denying that the jet violated Turkish airspace.
Turkey's news agency said it crashed into Syrian territory close to the border with Turkey.
Rami Abdurrahman, who heads the Britain-based Syrian Observatory for Human Rights, said the warplane crashed in the Turkomen Mountains region in the coastal province of Latakia.
The Turkomen Mountains region has been subjected to a government offensive over the past days, under the cover of Russian airstrikes.