The European Commission said Tuesday it has opened an anti-trust probe against Russian energy giant Gazprom on concerns it is hindering competition in central and eastern European gas markets. The Brussels-based competition watchdog said in a statement that it notably suspected Gazprom "may have prevented the diversification of supply of gas" and "imposed unfair prices on its customers by linking the price of gas to oil prices." A Commission spokesman listed the countries concerned as Bulgaria, the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland and Slovakia. "It cannot be excluded that, depending on the results of the probe, it be extended to other countries," said Antoine Colombani, spokesman for competition commissioner Joaquin Almunia. A source close to the enquiry said Gazprom was suspected of trying to carve up the European market to enable it to set different prices from country to country -- earning huge profits in markets where it faced little or no competition. The move follows September 2011 inspections at gas company premises and comes amid recurrent concerns that lower gas supplies from Russia could spell potentially higher prices for consumers. The EU imports 60 percent of its gas needs, with a quarter of gas consumed supplied by Russia. "An opening of proceedings does not prejudge the outcome of the investigation," the Commission statement said. "It only means that the Commission will treat the case as a matter of priority." The bloc has frequently found itself at loggerheads with Moscow over energy supply. Lithuania notably has repeatedly locked horns with Gazprom, its only gas supplier, over what it claims is unfair pricing -- a charge the Russian group denies.