Yuganskneftegaz was purchased at auction Sunday by Baikal Finance Group, which bought 76.79 percent of Yukos' core asset for $9.3 billion, payable Jan. 2.
But no one knows who is behind the group. The government of Vladimir Putin denies any involvement, as does the official Gazprom energy company, Itar-Tass said Monday.
Spokesmen for Lukoil, TNK-BP, Sibneft and Surgutneftegaz also told the Novosti news agency their companies had no relation to Baikal.
Representatives of Yugansk's new owner refused to participate in a press conference summing up the auction, and Novosti said reporters could not physically find a company located at the address on the formal bid.
Analyst Ronald Smith of Renaissance Capital told Itar-Tass he doubted the company would be able to pay the bid, and said he expected a new auction would be probably called.
Yukos' troubles began more than a year ago when its key shareholders were arrested, including founder Mikhail Khodorkovsky, now on trial on in Moscow on separate charges of tax evasion and fraud.