- Russia's Gazprom said it cut gas supplies to Poland and Bulgaria after they refused to pay in rubles.
- The UK's deputy prime minister accused Russia of "bullying" the countries over energy.
- Dominic Raab said Britain would stand "shoulder to shoulder" with them, warning the move would backfire.
Russia is "bullying" Bulgaria and Poland by cutting off the countries' gas supply, the UK's deputy prime minister said.
The Russian energy giant Gazprom enacted Moscow's threat to halt supplies to the two countries on Wednesday after they refused to pay for its energy in rubles, as had been demanded of "hostile countries" by President Vladimir Putin.
In a statement, Gazprom said it had "completely suspended gas supplies to Bulgargaz (Bulgaria) and PGNiG (Poland)" and further warned that transit via Poland and Bulgaria would be cut if gas was taken illegally.
The decision followed Poland's announcement that it was imposing sanctions on 50 entities and individuals, including Gazprom, Russia's biggest gas company.
Dominic Raab, Britain's deputy prime minister and justice secretary, told Sky News Wednesday morning that the UK would stand "shoulder to shoulder" with the two countries.
"We need to show solidarity. Clearly what we're seeing is the need to wean ourselves off reliance on Russia. We have been warning about this for a while, but yes, we'll stand shoulder to shoulder with our Polish friends and allies," he said.
Raab warned the move would backfire on Russia, making the country "not just a political pariah, but an economic pariah."
"One thing is true and clear. We cannot allow [Putin's] bullying behavior, whether it is economic warfare, or it is military warfare, to succeed," he said.
Russia's move was also attacked by Andriy Yermak, the chief of staff to Ukraine's President Volodymyr Zelenskyy, who said Russia was "beginning the gas blackmail of Europe."
Yermak called on the European Union, of which Poland and Bulgaria are members, to "be united and impose an embargo on energy resources, depriving the Russians of their energy weapons."
And Ursula von der Leyen, the president of the European Commission, vowed solidarity as she condemned the move as "yet another attempt by Russia to use gas as an instrument of blackmail."
"This is unjustified and unacceptable, and it shows once again the unreliability of Russia as a gas supplier," she added. "We are prepared for this scenario. We are in close contact with all member states."
UK Prime Minister Boris Johnson has repeatedly called for Europe to wean itself off Russian energy, with Germany coming in for particular criticism over its reliance.
On Tuesday night Poland's minister for climate and environment, Anna Moskwa, moved to reassure citizens that the country had "the necessary gas reserves and sources of supply that protect our security — we have been effectively independent of Russia for years," local media reported.
"There will be gas in Polish homes," she said.