VTB, however, has denied to Reuters taking any part in the deal.

"VTB has not issued and is not planning to issue a loan to QIA to finance the acquisition," the bank said in response for a request for comment.

The Reuters sources, however, claim VTB provided a US$6 billion loan to the Qatar sovereign wealth fund that teamed up with Swiss Glencore to acquire 19.5 percent in Rosneft last year.