Gazprom Media is expected to pay $15 million for the Internet resource, a Russian equivalent of the U.S. site YouTube, which allows users to upload videos for general viewing, Kommersant said.
RuTube owners Oleg Volobuyev and Mikhail Paulkin, who are believed to retain stakes in the venture, have neither confirmed nor denied the deal. Gazprom Media said it was too early to comment, the paper said.
Analysts said the Internet resource is heavily overpriced, but admit that valuing it is difficult.
"I believe the company has been overvalued," said Roman Simonov, managing director of Delta Private Equity Partners investment fund, quoted by the paper. "But it is difficult to give a fair price as it is based on growth expectations for Internet advertising."
RuTube.ru is currently visited by some 5.5 million people per month, or 400,000 daily, compared with around 150,000 visitors per day last July.
Former RuTube designer Askar Tuganbayev told the paper the portal could stop being available to downloads by Internet users and be turned into "a sort of branch of the TNT channel" controlled by Gazprom Media.
Gazprom has been criticized for its buyouts of media critical of the Kremlin. The monopoly has bought controlling stakes in the NTV television channel from exiled media tycoon Vladimir Gusinsky, in Kommersant, five radio stations including Ekho Moskvy, and acquired a series of other media assets.
Echoing Tuganbayev's fears, Nikolai Mityushin, head of investment at ABRT venture fund, said: "They are not after [the portal's] content downloaded by users. Gazprom Media needs a springboard to start online broadcasting."
The banker said the company's emergence on the Internet is a logical step considering growing Internet video ratings.