The president of the European Commission, Ursula von der Leyen, warned EU importers Wednesday that paying for Russian gas in rubles, as the Kremlin has demanded, would breach sanctions, AFP reported.

Brussels' top official told reporters that, unless a supply contract was denominated in rubles, European firms must not bow to pressure to pay in the Russian currency.

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"This would be a breach of the sanctions, so a high risk for the companies," she said.