Russia warned Europe on Friday that Moscow could cut off its gas supplies because some European countries have been re-exporting gas to Ukraine to help Kiev through its latest energy war with Moscow.

Russia warned Europe on Friday that Moscow could cut off its gas supplies because some European countries have been re-exporting gas to Ukraine to help Kiev through its latest energy war with Moscow.

The threat came as energy chiefs gathered in Berlin for EU-mediated talks aimed at halting a Russian gas supply cut to Ukraine that could leave parts of the war-scarred nation without heat this winter.

Energy Minister Alexander Novak said the re-export to Ukraine of gas Europe buys from Russia was illegal and could see some of its nations go without fuel shipments from state energy giant Gazprom for the first time since 2009.

"The agreed contracts do not foresee a re-export," Russian Energy Minister Alexander Novak told Friday's edition of Germany's Handelsblatt business daily.

"We hope that our European partners will stick to the agreements. That is the only way to ensure there are no interruptions in gas deliveries to European consumers."

Novak's comments were published only hours after Ukraine's state energy firm Naftogaz reported an unexplained interruption of gas supplies it receives through Hungary.

Naftogaz noted that the apparent cut "came only a few days after a visit to Hungary by representatives from (Russian state gas firm) Gazprom."