Russia said Tuesday one of its Su-24 fighter jets was shot down along the border between Turkey and Syria, but said "firing from the ground" was responsible for downing the plane.
Turkish military officials, however, said their F-16 jets shot down the plane after it violated the country's airspace and ignored 10 warnings in the span of five minutes to leave.
Russia's defense ministry said the jet never left Syrian territory. Russia also said its pilots ejected, but that their status was unknown. Video from the area appeared to show two pilots parachuting down from the sky, and Turkey's Dogan news agency said Russian helicopters were searching the area.
A Kremlin spokesman called it a "very serious incident" but said it was too early to draw conclusions.
A U.S. State Department spokesman says they cannot confirm press reports that Turkish jets have downed a warplane of unknown origin, but are monitoring the situation closely.