Russian President Vladimir Putin has accused the Turkish government of attacking its jet to protect the illegal oil trade with Islamic State .

It is the latest barb in an increasingly hostile war of words between the Russian and Turkish leaders since Turkey shot down a Russian jet on November 24.

Turkey denies it trades with IS and Mr Erdogan has challenged Mr Putin to prove his allegations.

BBC Moscow Correspondent Sarah Rainsford and BBC Turkey Correspondent Mark Lowen explain what is going on behind the heated rhetoric.