Russian President Vladimir Putin said the plane had been attacked when it was 1 km (0.62 mile) inside Syria and warned of "serious consequences" for what he termed a stab in the back administered by "the accomplices of terrorists".

"We will never tolerate such crimes like the one committed today," Putin said, as Russian and Turkish shares fell on fears of an escalation between the former Cold War enemies.

Each country summoned a diplomatic representative of the other and NATO called a meeting of its ambassadors for Tuesday afternoon. Russia's Foreign Minister Sergei Lavrov cancelled a visit to Turkey due on Wednesday and the defence ministry said it was preparing measures to respond to such incidents.

Jim Paris Comments -

This could start World War III. There is no way Putin is going to sit back and not retaliate. Turkey is a member of NATO,  and as such we are obligated to consider any attack on them as an attack on the U.S.  Russia is fighting ISIS, and even if there was a small incursion on their border, there was no real military threat against Turkey. Put your seat belts on, this does not look good to me...