"A number of major European companies, including Germany's E.ON and Finland's Fortum, as well as UC RusAl, are showing an interest in OGK-4's offer of new shares. Participation by Italy's Enel is also not ruled out," the source said.
But a spokesman for Russian aluminum giant UC RusAl said the company has no plans to participate in the bidding.
OGK-4's owner, electricity monopoly RAO UES, approved a plan to offer 23 million new shares in the generation company in February, or 46.81% of pre-placement charter capital.
OGK-4's charter capital totals 19.65 billion rubles ($770 million). RAO UES holds 89.6% of the company's stock, and minority shareholders own 10.4%.
Registered on March 4, 2005 in the city of Surgut, in West Siberia's Khanty-Mansi Autonomous District, OGK-4 incorporates five thermal power plants: one in Western Siberia, one in the Far East, two in central Russia and one in the Perm Territory in the Urals.
