This story is unfolding as this article is going to press. What we know now is that Turkey shot down a Russian warplane near the Syrian border. Vladimir Putin offered strong remarks, saying it will have "serious consequences for Russian-Turkish relations."
There is already talk of economic fallout as a result of this incident. It is being suggested that recent air strikes in Syria conducted by Russia, as a result of the Paris attacks several weeks ago, could have provoked the Turkish leadership to retaliate by shooting down the Russian plane.
Source - NY Times
The president of Russia, Vladimir V. Putin, said Turkey's shooting down of a Russian warplane was a “stab in the back.” The prime minister of Turkey, Ahmet Davutoglu, asserted the nation's right to respond when its airspace has been violated.
ISTANBUL — Turkish fighter jets on patrol near the Syrian border on Tuesday shot down a Russian warplane that Turkey said had ignored numerous warnings and violated its airspace, in a long-feared escalation that will further strain relations between the NATO member country and Russia.