In Paris on Monday, Russian President Vladimir Putin accused Turkey of shooting down a Russian warplane near its border with Syria because the country is involved in oil trade with the 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," Putin said.
ISIS brings in millions of dollars a month by selling oil illegally, and Putin said he had information that shows ISIS oil is passing through Turkish territory, the BBC reports.
Turkey, which is part of the U.S.-led coalition carrying out airstrikes against ISIS, denies having ties to the group.
Turkey says the Russian jet entered its airspace Nov. 24, while Russia insists it didn't; one pilot was killed and the other rescued.