Russian President Vladimir Putin said Monday that Turkey had shot down an Su-24 bomber , which Ankara insists violated its airspace, in order to protect supplies of oil from the self-styled "Islamic State."

"We have every reason to think that the decision to shoot down our plane was dictated by the desire to protect the oil supply lines to Turkish territory, right to the ports where it is loaded onto tankers," Putin told reporters in Paris on the first day of the UN climate conference.

Revenue from seized oil fields in Syria and Iraq is one of the main sources of income for IS.

Turkish President Recep Tayyip Erdogan responded by offering to resign if the allegations could be proved.