The energy war between Russia and the European Union entered a new and more intense phase Wednesday after Russian gas giant Gazprom announced it shut off supplies to customers in Poland and Bulgaria.

Gazprom said the shut-off will continue “until the payments are made” with the Russian ruble, a condition for purchases that Russian President Vladimir Putin introduced in the last month to force the hand of “unfriendly” nations of the West. It is the first such shut-off since Russia’s invasion tanked relations between the interdependent fossil fuel producer and the EU.