EU antitrust authorities are likely to intensify the collection of information on Gazprom's activities in Europe, Reuters reported, citing a source.

Last month, EU antitrust chief Margrethe Vestager said she had sent a request to gas companies, including Gazprom, for restricted supplies after accusations that the Russian gas giant was withholding additional production that could be run to lower rising prices. Gazprom denies such allegations.

The EU competition commissioner has not yet made a final decision on the next phase of the investigation, the source said.

The European Commission declined to comment, saying the investigation was ongoing.

Gazprom has said that the Russian gas company supplies gas in excess of its contracts when it has requests.

Fatih Birol, head of the International Energy Agency, said last month that Russia was contributing to Europe's under-supply of natural gas.