Russian Prime Minister Vladimir Putin has said his government is keeping a close eye on raids by the European Commission on Gazprom and its subsidiaries, according to reports.
Putin also said the Russian gas giant would be co-operating with the investigators.
"The government of Russia will follow what is going on around Gazprom in the most attentive way," Putin said, Reuters reported, citing Russian news agency Interfax.
Speaking after a meeting at his residence at Novo-Ogaryovo outside Moscow with Gazprom chief Alexei Miller, Putin said it was "necessary to cooperate", and told Miller to keep him informed about the situation.
The European Commission raided offices of Gazprom subsidiaries in central and eastern European states last week as part of an investigation into firms involved in the supply, transmission and storage of natural gas.
The commission has said the raids were linked to suspicions about anti-competitive practices, without elaborating further.
Ssources on both sides have attributed the raids to EU efforts to reduce reliance on Russian gas, which makes up about a quarter of Europe's supplies, according to Reuters.
A source at Gazprom has said he suspects the raids may be linked to the company taking a step forward in implementing its South Stream pipeline project, a rival to the EU-backed Nabucco pipeline project.
The South Stream pipeline, which will bring gas from Russia to Bulgaria and on to Greece, Italy and Austria, is due to be completed in 2015.
South Stream aims to deliver 63 billion cubic metres per annum of Russian gas via the Black Sea to Europe by 2020.
Gazprom has set up joint ventures with companies in Austria, Bulgaria, Croatia, Greece, Hungary, Serbia and Slovenia for the onshore section of the pipeline.
The raids were also conducted ahead of November's start-up of Russia's Nord Stream pipeline to Germany, which will have a capacity of 55 billion cubic metres.
Miller said the raids on Gazprom subsidiaries were "an unpleasant surprise", adding that he company was ready to defend its rights according to law, Interfax reported.
The company defended its operations last week, stating that the gas giant "could not offer the cooperation needed to address all possible issues" because it was not given advance warning of the operation.
Gazprom insisted its European gas-supply contracts are in "full compliance" with international law.