Gazprom's oil unit head Sergei Bogdanchikov said this week that the aim was to build a world-class company like Exxon Mobil Corp.

Gazprom, which owns Russia's gas pipelines and is the monopoly gas exporter, also plans to buy Rosneft, a state-owned oil company. Surgutneftegaz, the fourth-largest oil company in Russia, and Sibneft, could also be targets, according to Bogdanchikov.

Six global investment banks are ready to lend Gazprom US$13 billion to fund the takeover of the main production unit of Yukos, Russia’s biggest oil company, the Financial Times reports.

A loan syndicate including Deutsche Bank, along with ABN Amro, BNP Paribas, Calyon, Dresdner Kleinwort Wasserstein and JPMorgan, is expected to extend Gazprom the single biggest emerging markets loan, according to the newspaper.

This will enable Gazprom's bid for Yuganskneftegas, which is facing a forced sale on December 19 as Russian authorities dismantle Yukos in pursuit of back tax claims now totalling more than $US5 billion ($A6.47 billion).

Meanwhile, hedge fund managers have channelled up to $4bn (£2bn) into Gazprom, the Russian gas monopoly, in the expectation that a barrier to foreign investment will be lifted.

In September Gazprom chief executive Alexei Miller said he expected restrictions on foreign investment to be lifted by the end of this year, ending the two-tier structure and creating a single class of shares. If that happened, rouble-denominated shares would jump in value as foreign investment became easier.

But the timetable for easing controls could yet shift, pending Gazprom's takeover of Yuganskneftegas, and the sale itself is not yet a foregone conclusion. Bloomberg reports that some Russian government officials now doubts whether so much power should be concentrated within Gazprom.

The Paris-based International Energy Agency, an energy policy adviser to 26 industrialised countries, shares these concerns, fearing that the takeover would would reduce competition.

"It is not good for the Russian energy market because the economic efficiency will lose – competition is going to more or less disappear," IEA senior economist, Fatih Birol, said at a London media briefing.

“A big part of the energy supply chain will be under the control of one single monopoly," Birol said.