Turkey has challenged Russia to prove its claim that Ankara shot down a Russian plane in order to protect its oil trade with Islamic State. “If you allege something you should prove it,” Turkish President Recep Tayyip Erdogan said. He was responding to the accusation by Russian President Vladimir Putin, who also said last week’s downing of the plane was a “huge mistake.” “You should put your documents on the table if you have any. Let’s see the documents,” Mr Erdogan said. “We are acting with patience. It is not positive for the two countries which have reached a position which could be regarded as a strategic partnership to make emotional statements.” President Erdogan also vowed to step down if the allegation that Turkey was buying oil from IS proved true, suggesting that President Putin should do the same if he was wrong. IS earns much of its money from illegal sales of oil. “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,” Mr Putin said at a news conference in Paris on Monday.