Cleary Gottlieb Steen & Hamilton is advising Russian telecoms giant MegaFon on its potential £2.5bn London initial public offering (IPO).

MegaFon, Russia's second largest mobile phone operator, was taken over this April by AF Telecom – the holding company of Russian businessman Alisher Usmanov. The company has since filed for permission to float a 20% stake, which could be worth as much as $4bn (£2.5bn).

MegaFon has reportedly asked Russia's financial markets regulator to list up to 123 million shares, although the company said the timing of the public offering would depend on market conditions.

Goldman Sachs and Morgan Stanley are leading the IPO, which would be the world's largest since Facebook's $16bn (£10bn) listing on the Nasdaq in May, and the largest IPO by a Russian company since VTB Bank raised $8bn (£5bn) in 2007 through a 22.5% London float.

Cleary, which declined to comment on its involvement in the listing, has well-respected capital markets teams in both London and Moscow. In December 2010 the firm advised Megafon on its $1.5bn (£900m) London-listed programme for loan participation notes.

Writing for Legal Week earlier this year, Cleary partner Simon Jay said the demand for English law advice from Russian clients was part of a "rapid increase" in cross-border financing work at the firm.

Usmanov – one of Russia's richest men – has several global business interests, including mining conglomerate Metalloinvest, an investment holding subsidiary of Gazprom, and Russian newspaper Kommersant, which was purchased from oligarch Boris Berezovsky in 2006.

Law firms Usmanov has worked with in the past include Field Fisher Waterhouse, which represented the billionaire on his acquisition of a £75m stake in Arsenal Football Club in 2007.

For more, see Field Fisher in for Arsenal stake sale to Russian.