MOSCOW - Russia’s defence ministry on Wednesday accused Turkish President Recep Tayyip Erdogan and his family of involvement in illegal oil trade with Islamic State jihadists, as a dispute rages over Ankara’s downing of one of Moscow’s warplanes.

“The main consumer of this oil stolen from its legitimate owners Syria and Iraq is Turkey. According to available information, the highest level of the political leadership of the country, President Erdogan and his family, are involved in this criminal business,” deputy defence minister Anatoly Antonov told journalists.

Ties between Turkey and Russia have shattered after Ankara shot down the jet on its border with Syria last Tuesday, with President Vladimir Putin accusing Ankara of downing the plane “to protect the oil supply lines to Turkish territory”. Erdogan has rubbished earlier Russian claims that Turkey is involved in the illegal oil trade with groups, including IS, in Syria and Iraq, insisting he would resign if allegations were proved true.

“Today we are presenting only part of the facts in our possession, that there is a unified team of bandits and the Turkish elite working in the region to steal oil from its neighbours,” Antonov said at the packed press conference in the defence ministry. “This oil enters the territory of Turkey in huge quantities, on an industrial scale along a living pipeline of thousands of oil tankers,” he said. Antonov claimed that “terrorists in Syria” earned $2 billion from the illegal oil trade and “that is why IS so protects its thieving oil extraction infrastructure in Syria and Iraq.”

In the meanwhile, Erdogan accused Russia of “slander” on Wednesday over Moscow’s allegations Turkey had bought oil from Islamic State (IS) 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 IS, 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 by Turkish fighter jets of a Russian warplane 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 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.”