The European Union said on Thursday it was preparing to charge Gazprom in an anti-trust probe on concerns the Russian energy giant was hindering competition in central and eastern Europe.

"We are now preparing the statement of objections," EU Competition Commissioner Joaquin Almunia told reporters in Lithuania, current holder of the EU's rotating presidency.

The so-called statement of objections is a formal step which allows the concerned party to reply, with a final decision only coming after it has made its defence.

Almunia refused to comment on a possible date for the statement, saying he "had no deadlines for this investigation".

But Lithuania's President Dalia Grybauskaite, herself a former EU budget commissioner, said in a press release on Thursday that the anti-trust probe was "anticipated to end in spring 2014."

EU energy chief Gunther Oettinger said last month that "experts will come to an analysis in the next six months".

Brussels launched its probe into Gazprom's use of long-term contracts in September 2012 over suspected infringement of EU competition rules in member states including Bulgaria, the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland and Slovakia.

"For Lithuania, gas prices increased by 600 percent between 2006 to 2012," Prime Minister Algirdas Butkevicius said Thursday, speaking along side Almunia.

"Such prices do have an impact on competitiveness," he said.