Last week, President Erdogan said Turkey only bought oil from legitimate sources and was taking steps to combat smuggling. He called on those making the allegations to provide proof and said he would resign if the claims were shown to be true.
Plane shot down
Moscow’s relationship with Ankara has deteriorated since Turkey shot down a Russian military plane on the Turkey/Syria border that it said had strayed into Turkish air space.
Last week’s confrontation is the most serious between a Nato member (Turkey) and Russia in half a century.
Russia and Turkey are also at odds over the Assad regime in Syria, which Moscow is trying to bolster and Ankara would like to see removed.