Russia threatened economic retaliation against Turkey on Thursday and said it was still awaiting a reasonable explanation for the shooting down of its warplane, but Turkey dismissed the threats as "emotional" and "unfitting".<br />In an escalating war of words, President Tayyip Erdogan responded to Russian accusations that Turkey has been buying oil and gas from Islamic State in Syria by accusing Syrian President Bashar al-Assad and his backers, which include Moscow, of being the real source of the group's financial and military power.<br />The shooting down of the jet by the Turkish air force on Tuesday was one of the most serious clashes between a NATO member and Russia, and further complicated international efforts to battle Islamic State militants.<br />World leaders have urged both sides to avoid escalation.
