Federal energy agency chief Sergei Oganesyan said that state-owned oil firm Rosneft had used financing from Russian banks for its 9.35-billion-dollar (7.2-billion-euro) acquisition of Yuganskneftegas in December.

"They reached an agreement with Russian banks," he said.

However, the official added that Rosneft had also signed a long-term contract for oil deliveries worth six billion dollars with energy-hungry China, the world's second-largest oil consumer which is keen to reduce its reliance on the Middle East.

"The Chinese company CNPC has made a pre-payment for long-term oil deliveries," he told journalists, without specifying if the entire sum was paid up front and the timespan of the oil contract.

Last month Russian newspaper Vedomosti reported that China's state-owned oil and gas giant could help Rosneft pay for the main Yukos subsidiary by offering a six billion dollar credit in return for oil.

The respected business daily quoted Russian government officials as saying that the China National Petroleum Corp had offered to help pay for Rosneft's purchase of Yuganskneftegas at a controversial auction in exchange for oil shipments.