Russia has alleged that Turkey is buying crude oil from ISIS?
- How does one verify that allegation?
- Is there any proof provided by Russia for that allegation?
- Are there any open source investigations(map routes, photographs etc) to prove the same?
Although I like the answer from @user3765080, I think that this question requires a definitive answer and the answer should be yes. If we ask about Turkey, we mean all the people of Turkey whether they are criminals or not. And buying oil from a terrorist organization is obviously criminal.
To whom does the Islamic State sell their oil? Sep 23, 2014.
Islamic State oil is being sold to organized criminals in Turkey. -- John Woo
To my knowledge, new & tangible information has not emerged since this question was previously answered, so I'll summarize.
Islamic State oil is being sold to organized criminals in Turkey . . . It is an open question to what extent Turkey is deliberately allowing this to occur. -- John Woo
I can't say if they are supporting them but they have some common interest . . . * . . . To sum it up, no they are not sympathizer of the Islamic State. They are mostly neutral toward them. -- Vincent
This skips four good paragraphs by Vincent, so for more information I recommend reading the entire answer.
Turkish businessmen struck lucrative deals with Isis oil smugglers, adding at least $10m (£6.6m) per week to the terror group’s coffers, and replacing the Syrian regime as its main client. Over the past two years several senior Isis members have told the Guardian that Turkey preferred to stay out of their way and rarely tackled them directly. -- The Guardian, quoted by bytebuster
And the following paragraph was not quoted, but was in one of bytebuster's sources.
Elaborate trade networks have also evolved, with oil being smuggled across borders in plastic jugs and transported by trucks and on donkeys into Iraq and Turkey. -- NY Times
IN SUMMARY: "It is an open question to what extent Turkey is deliberately allowing this to occur."