European gas prices up 24%. Ruble reaches 2-year high against the euro.
Germany must prepare "intensively" for gas shortages, says EnBW - one of the largest energy supply companies.
Greece said on Wednesday it would offer help to Bulgaria after Russia cut off its gas supply, and that it will make its own next payment to Russian gas producer Gazprom at the end of May, as scheduled.
Greece relies on Russian gas for more than 30% of its annual energy needs and has a contract that runs until 2026.