Russia's defence ministry officials claim to have proof Turkey is involved in oil trading with the Islamic State (Isis) and has accused president Recep Tayyip Erdogan and his family of illegal business dealings with the jihadist group.
During a press conference in Moscow, the officials cited satellite imagery which they said showed oil tanker trucks heading from IS territory to Turkey and said they knew of three routes by which oil has passed into Turkey.
They said Russia's air strikes in Syria helped to "almost halve" illegal oil turnover, destroying 32 IS oil refineries in two months. Admitting that Erdogan will not admit oil smuggling "even if his face is smeared in it", the ministry officials said they will present detailed information on the illegal trading next week.
"We have evidence based on air intelligence that Turkey is directly involved in trade of illicit oil," they said while showing the alleged routes of oil transportation and footage of vehicles moving through Syrian-Turkish border.
"Terrorism without money is like an animal without teeth," they said.
Erdogan earlier said he was ready to quit office if his Russian counterpart Vladimir Putin provides evidence for his allegations that Ankara trades oil with IS. His comments came after Putin accused Turkey of downing the Russian Su-24 war plane last week to IS oil supplies.
"I will say something very strong here," Erdogan was quoted as saying by the state-run Anadolu news agency in Paris. "If such a thing is proven, the nobility of our nation would require that I would not stay in office."
He claimed that Turkey obtained all its oil and gas imports "through the legal path". "We are not dishonest so as to do this kind of exchange with terrorist groups," he continued. "Everyone needs to know this."
It is not the first time that claims of Turkey trading oil with IS have surfaced.
Last summer, the Guardian's Martin Chulov reported that US special forces raided the compound of an IS leader in eastern Syria who was responsible for oil smuggling. Abu Sayyaf, a Tunisian fighter, were allegedly in charge of the black market oil, with Turkish buyers among its main clients.
One Western official told the Guardian that direct dealings between Turkish officials and IS members were "undeniable".
In 2014, a member of Turkey's parliamentary opposition claimed that IS had smuggled $800m worth of oil into Turkey from Syria and Iraq, according to Al-Monitor.
An Iraqi member of parliament backed the claim saying that Syrian and Iraqi oil were carried by trucks from those countries through the borders to Turkey and sold at less than 50% of the international price.