If you thought the back-and-forth in the bloody soap opera that is the Russia-Turkey tussle was over, it’s not.

Wednesday saw yet more fireworks, this time from the Russian military and the Kremlin itself, who doubled down on their boss Vladimir Putin’s claims and went a step further, accusing the president of Turkey — Recep Tayyip Erdogan — and his family of personally profiting from an under-the-table oil deal with ISIS (Islamic State).

As you may remember this whole thing started when Turkish forces shot down a Russian warplane they said had entered their airspace.

It was the first time a NATO member had shot down a Russian aircraft in more than 50 years.

This from The New York Times:

The Russian Defense Ministry invited dozens of foreign military attaches and hundreds of journalists to produce what they said were satellite and aerial images of thousands of oil trucks streaming from the IS-controlled deposits in Syria and Iraq into Turkish sea ports and refineries.

“The main customer for this oil stolen from Syria and Iraq is Turkey,” said Deputy Defense Minister Anatoly Antonov. “The top political leadership of the country, President Erdogan and his family, is involved in this criminal business.”

The Turkish leader has denied Russian President Vladimir Putin’s earlier claims of Turkey’s involvement in oil trade with the IS, and has pledged to step down if Moscow proves its accusations.

“No one has the right to make such a slander as to suggest that Turkey buys Daesh’s oil. Turkey has not lost its moral values as to buy oil from a terror organization,” Erdogan said in Wednesday’s speech at Qatar University, using the Arabic acronym for the Islamic State group, shortly after the Russian Defense Ministry made the claims. “Those who make such slanderous claims are obliged to prove them. If they do I would not remain on the presidential seat for one minute. But those who make the claim must also give up their seat if they can’t prove it.”

Erdogan also threatened that if the trash talking doesn’t stop, his nation will “be forced to take its own measures”. Considering Turkey relies on Russia economically so much more than vice versa (and Putin has, since the warplane downing, enacted strict sanctions) it seems like it would be easy for the former Soviet Union to call Erdogan’s bluff on the vague threat.

With so much more flavor than Putin, Antonov laid the slander on Wednesday extra thick, saying that ISIS made about a $2 billion a year selling oil, and that most of it was Turkey’s cash.

He also dryly quipped about the Turkish leader’s commercial acumen.

“What a great family business!” Antonov said. “Obviously, no one but the closest people could be entrusted to control such dealings.”

United States State Department spokesman Mark Toner, however, doused water on the fire Russia was blowing, and said the rumors were completely bogus.

“We never said oil smuggling from ISIL [ISIS] is not a problem,” he said. But “there is no Turkish government complicity in some operation to buy illegal oil from ISIL [ISIS]. We just don’t believe that to be true in any way, shape or form.”

Turkey is part of the U.S.-led coalition airstrikes on ISIS in both Syria and Iraq.