The European Commission announced it was opening an antitrust investigation into Gazprom. European consumers get about 20 percent of their natural gas from Russian suppliers though 80 percent of that runs through the Ukrainian gas transit system.
The Russian company, in a statement, said it "scrupulously" meets the letter of the law in all countries where it conducts business.
"Gazprom Group's activities on the EU market are in full conformity with legal standards applied by other natural gas producers and exporters, this includes price formation mechanisms," the statement read.
The European Commission said it was concerned that Gazprom abused its market position in the upstream natural gas sector in Central and Eastern Europe, adding the company might be interfering with competition in the regional gas market.
Russia's state-run news agency RIA Novosti reports that shares in Gazprom dropped 2 percent following the news of the antitrust investigation.
Gazprom said it would work in good faith with the commission and is committed to a constructive dialogue.