By Foo Yun Chee and Andrius Sytas

VILNIUS (Reuters) - The European Union's antitrust chief said on Thursday that he was ready to charge Gazprom <GAZP.MM> with anti-competitive practices in a move that could lead to a fine of up to $15 billion for the Russian gas export monopoly.

The European Commission opened an investigation more than a year ago after raiding the offices of several Gazprom units in central and eastern Europe, where it said it had concerns the company might have abused its dominant position.

The EU antitrust regulator said Gazprom may have hindered the free flow of gas across the EU's 27 countries and imposed unfair prices on its customers by linking the price of its gas to oil prices.

Speaking at a conference in the Lithuanian capital Vilnius, Almunia said the EU's executive was preparing a charge sheet against Gazprom, known as a statement of objections.

"It would be premature to anticipate when the next steps would be taken in this investigation, but we have now moved to the phase of preparing a statement of objections," EU Competition Commissioner Joaquin Almunia told a conference organized by the Lithuanian Competition Authority.

He said the investigation covered Estonia, Latvia, Lithuania, Poland, the Czech Republic, Slovakia, Hungary and Bulgaria.

Gazprom generated 4.76 trillion roubles ($148 billion) in revenues last year. Companies can be penalized up to 10 percent of their annual revenues for breaching EU antitrust rules. ($1 = 32.2147 Russian roubles)

(Reporting by Foo Yun Chee and Andrius Sytas; editing by Charlie Dunmore)