Russia's decision to stop delivering gas to customers in Europe is "an instrument of blackmail", European Commission chief Ursula von der Leyen has said.
The move is "unjustified and unacceptable" and shows the unreliability of Russia as a gas supplier, she added.
She said that EU member states have contingency plans in place for this scenario and the European Commission is in close contact with them to ensure alternative deliveries and the best possible storage levels across the bloc.
A meeting of the gas coordination group is taking place now to map out the EU's coordinated response, von der Leyen adds.
"We will also continue working with international partners to secure alternative flows - and I will continue working with European and world leaders to ensure the security of energy supply in Europe," she said.
"Europeans can count on our full support."
Russia opened a new front in its war over Ukraine on Wednesday, deciding to shut off gas to two European Union nations that staunchly back Kyiv, a dramatic escalation in a conflict that is increasingly becoming a wider battle with the West.
One day after the United States and other Western allies vowed to speed more and better military supplies to Ukraine, the Kremlin upped the ante, using its most essential export as leverage. European gas prices shot up on the news.
The escalation came in a memo from state-controlled Russian giant Gazprom, which said it had cut natural gas deliveries to Poland and Bulgaria because they refused to pay in Russian rubles, as President Vladimir Putin had demanded. The company said it had not received any payment since the beginning of the month.
Gazprom’s decision to cut gas to two European countries was another dark turn in the war, which has revived the geopolitical rifts of the Cold War and had an immediate impact. European gas prices spiked by as much as 24%.
Fatih Birol, the executive director of the Paris-based International Energy Agency, called the move a “weaponization of energy supplies” in a tweet.
While Poland and Bulgaria are the first in the EU to have their Russian gas supplies cut off, they're not the only countries to have refused Moscow's demand that deliveries be paid for in roubles - which Gazprom says is the reason it's turned off supplies this morning.
Other countries report that they are continuing to receive gas normally include:
Austria, which has continued paying for its Russian gas in euros, said this morning that supplies were continuing unrestricted. It receives around 80% of its gas from Russia.
Similarly, Germany has also refused to pay for its gas in roubles. Last night its network regulator said it was monitoring the situation but said the security of its supplies was "currently guaranteed."
The only EU country to offer to pay for its Russian gas in roubles is Hungary. Its foreign minister said this morning that supplies were normal, adding that in May it would be transferring its next payment for Russian gas in euros for Gazprombank to then convert it into roubles.
Poland’s prime minister has lashed out at Russia for trying to “blackmail” his country with an abrupt cutoff of gas supplies. He says he believes the move was revenge for new sanctions that Warsaw imposed this week against Russia.
The sanctions announced Tuesday targeted 50 Russian oligarchs and companies, including Gazprom. Hours later Poland said it had received notice that Gazprom was cutting off supplies to Poland for failing to comply with new demands to pay in Russian rubles.
Speaking to the Polish parliament, Prime Minister Mateusz Morawiecki vowed that Poland would not be cowed by the gas cutoff. He said Poland was safe thanks to years of efforts aimed at securing gas from other countries.
Lawmakers stood and applauded when he said that Russia’s “gas blackmail” would have no effect on his country.
Russian made up some 45% of Poland’s overall gas usage until the cutoff. But Poland is far more reliant on coal to heat homes and fuel industry, with gas accounting for only 9% of the country’s overall energy mix.
Russian supplies were also due to end later this year in any case. Poland has made plans to get its supplies from other countries, including Norway. A new pipeline, “Baltic Pipe,” is due to become operational in the fall.