The shooting down of a Russian warplane by Turkish fighter jet last month has strained relations between Moscow and Ankara. (AFP Photo)
Turkish President Recep Tayyip Erdogan accused Russia of "slander" on Wednesday over Moscow's allegations that Turkey had bought oil from Islamic State of Iraq and the Levant (ISIS) jihadists in Syria.
"No one has a right to engage in slander against Turkey by saying that Turkey is buying oil from Daesh (IS)," Erdogan said in comments broadcast by Turkish television on a visit to Qatar.
He was speaking after the Russian Defence Ministry claimed Erdogan and his family were involved in the illegal oil trade with ISIS, raising the stakes in a week-long standoff after Turkey shot down a Russian war plane on the Syrian border.
Erdogan reaffirmed that he would resign if the allegations were proven to be true and appeared to suggest that Russian President Vladimir Putin should also consider his position.
"I won't stay in the seat of president for even one minute if Russia proved its claims. But those who spread this slander shouldn't retain their seats either."
"Turkey has not lost its moral values so as to buy oil from a terrorist organisation," he added.
The shooting down of a Russian warplane by Turkish fighter jets on the Syrian border on November 24 has plunged relations between Moscow and Ankara into their biggest crisis since the Cold War.
Turkey claims the plane was in its airspace and ignored repeated warnings but Russia insists it never crossed the border from Syria.
Russia -- Turkey's main energy supplier -- is also imposing sanctions against Turkey that will hurt its food exports and has also told Russian tourists not to visit the country.
"Adding fuel to the fire benefits no one," said Erdogan, who signed a memorandum of understanding on gas supplies from Qatar, Turkey's closest ally.
"We are saddened by the disproportional responses by Russia to an incident in which the whole world agrees we are right."
"If these responses continue, we will take our own measures," he said, without elaborating.
But Erdogan also said that Turkey had no intention of escalating the crisis and said the two countries still have potential for cooperation.
"We will use whatever diplomatic language international diplomacy requires. We don't want this problem to hurt our current relations or potential any further.