Russia opened a new front in its war in Ukraine on Wednesday, cutting two European Union nations that staunchly back Kyiv off from its gas, a dramatic escalation in the 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, which European leaders denounced as “blackmail.”

In a memo, state-controlled Russian giant Gazprom said it was cutting Poland and Bulgaria off from its natural gas because they refused to pay in Russian rubles, as President Vladimir Putin had demanded. The company said it had not received any such payment since the beginning of the month.

The gas cuts do not immediately put the countries into dire trouble since they have worked on getting alternative sources for several years now and the continent is heading into summer, making gas not as essential for households.

Still, it sent shivers of worry through the 27-nation European Union, which immediately convened a special coordination group to limit the impact of the move.

On the ground too, the geopolitical fight intensified, with the Russian military claiming Wednesday that its missiles hit a batch of weapons that the U.S. and European nations delivered to Ukraine.

A day earlier, explosions rocked the separatist region of Trans-Dniester in neighboring Moldova, knocking out two powerful radio antennas and raising fears the war could spill over Ukraine’s borders. No one claimed responsibility for the attacks — the second in as many days — but Ukraine all but blamed Russia.

And a Russian missile hit a strategic railroad bridge linking Ukraine’s Odesa port region to neighboring Romania, a NATO member, Ukrainian authorities said.

Just across the border in Russia, an ammunition depot in the Belgorod region was burning early Wednesday after several explosions were heard, the governor, Vyacheslav Gladkov, said on the messaging app Telegram.

Ursula von der Leyen, president of the European Commission, has condemned Russian for seeking to “blackmail” Europe after Russian energy giant Gazprom confirmed that it had cut gas supply to Poland and Bulgaria.

She said: “The announcement by Gazprom that it is unilaterally stopping delivery of gas to customers in Europe is 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.