The Turkish military have reportedly shot down a Russian military aircraft on the border with Syria.
Russia's defence ministry said an Su-24 had crashed on Syrian territory after being hit by fire from the ground, and that its pilots had managed to eject.
But Turkish military officials said Turkish F-16s had shot down the plane after repeatedly warning its pilots they were violating Turkish airspace.
Video footage showed the plane crashing into mountains in Latakia province.
The ministry stressed that "throughout its flight, the aircraft remained exclusively above Syrian territory", adding: "Objective monitoring data shows it."
However, Turkish military officials said its F-16s had fired on an unidentified aircraft after warning it 10 times in the space of five minutes about violating Turkish airspace.