UPDATE 1-MegaFon to start pre-marketing IPO Tuesday-sources

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MOSCOW, Oct 8 (Reuters) - MegaFon , Russia'ssecond-largest mobile phone operator, will start pre-marketingfor its London initial public offering on Tuesday, severalfinancial market sources said.

It is expected to make a statement announcing the IPO in thecoming days, a separate source familiar with the situation said.

The IPO will give investors the chance to buy into a Russiantelecoms company that is outpacing its peers in a growing homemarket, but unlike rivals is shielded from tricky overseasoperations and complex corporate disputes.

The cut-throat market is dominated by three players, MTS, MegaFon and Vimpelcom , which together control80 percent of the overall pie in Russia.

MegaFon, in which Russia's richest man Alisher Usmanov tookcontrol in April, received regulatory approval in September tolist 123.38 million shares, or 19.9 percent of the total, inLondon.

Analysts have estimated that the IPO could raise $3 billion,making it the biggest in London since trader Glencore's$10 billion IPO in May 2011 and the largest Russian market floatsince Rusal raised $2.2 billion in Hong Kong in 2010.

It is unclear whether MegaFon is still aiming to raise thatamount. The company was expected to meet with analysts onTuesday, a separate source familiar with the matter said.

MegaFon declined comment.

(Reporting by Olga Popova and Megan Davies; additionalreporting by Maria Kiselyova; Editing by Douglas Busvine)

((maria.kiselyova@thomsonreuters.com)(+7 495 775 1242)(ReutersMessaging: maria.kiselyova.thomsonreuters.com@reuters.net))