BRUSSELS — Reverberations from the Ukraine war widened on Wednesday, jolting energy markets and spilling across borders, as Russia responded to the West’s escalating arms shipments and economic penalties by halting gas supplies to two European nations and threatening further unspecified retaliation.
The European Union’s top official described as “blackmail” the announcement that Russia was suspending shipments of natural gas to Poland and Bulgaria. Though the immediate impact was likely to be limited, the cutoff was the Kremlin’s toughest retaliation yet against a U.S.-led alliance that President Vladimir V. Putin has accused of waging a proxy war aimed at weakening Russia.
Even as news of a U.S.-Russia prisoner exchange offered a glimmer of hope for diplomatic engagement, Mr. Putin warned that he would order more “counterstrikes” against any adversaries that “create threats of a strategic nature unacceptable to Russia.”
At the same time, a series of explosions across Ukraine’s borders stoked fears that the war, now in its third month, might spread. Blasts were reported in three Russian districts on Wednesday morning, and suspicion fell on Ukrainian forces, which are benefiting from increasingly sophisticated weapons and intelligence from the United States and its allies.
Those blasts came a day after explosions shook Transnistria, a pro-Russian breakaway region of Moldova, on Ukraine’s southwestern flank. Some analysts — and Ukrainian and Moldovan officials — said it was likely that Russia, which has thousands of troops in Transnistria, had orchestrated the explosions to create a pretext to invade Ukraine from that direction.
Taken together, the developments raised the risk of worse to come.
“What’s the ‘so what’ of this escalatory cycle? Further escalation becomes more likely as animosity builds,” said Cliff Kupchan, chairman of the Eurasia Group, a political risk consulting organization. “The chance that Russia hits a staging facility in Poland goes up. The risk that NATO supplies aircraft to Ukraine goes up. Ukraine could strike bigger targets in Russia. Moscow could cut gas to more European nations.”
Economists warned that Europe could face a sharp slowdown of growth if the cutoff of sales by Gazprom, Russia’s state-owned gas company, spreads — or if Europe imposes an embargo on Russian gas. European natural gas prices surged as much as 28 percent on Wednesday and the euro’s value fell below $1.06 for the first time in five years on rising concerns about energy security and a slowdown in European growth. The currency has fallen nearly 4 percent against the U.S. dollar in April alone.
Gazprom’s stated reason for halting gas deliveries was the refusal by Poland and Bulgaria to pay in rubles, a new requirement Russia announced last month, despite the fact that its foreign contracts generally call for payment in dollars or euros. Most European buyers have not complied, which would subvert European Union financial sanctions imposed on Russia after the Ukraine invasion and help prop up the battered ruble.
The European Union had been preparing for the possibility that Russia might halt natural gas deliveries, said Ursula von der Leyen, the European Commission president. Nonetheless, she told a news conference, the Russian move was an attempt “to use gas as an instrument of blackmail.”
Poland and Bulgaria will quickly receive gas supplies from neighboring E.U. countries to compensate for the loss of Russian gas, she said, declaring that “the era of Russian fossil fuels in Europe is coming to an end.”
Both Poland and Bulgaria said the Russian cutoff would have little impact. In Poland, where electricity is largely generated with coal, not gas, the government sought to assuage any public fears. Prime Minister Mateusz Morawiecki assured Poles that gas storage tanks were three-quarters full — much higher than in other countries.
And if the Kremlin’s plan was to intimidate Poland and Bulgaria with a future of unheated homes and cold meals in the hope of fracturing Western unity to aid Ukraine, it may have miscalculated. On a sunny spring day in Warsaw, the Polish capital, many people reacted with shrugs to the news — mixed with disbelief that anyone would ever view Russia as a trustworthy supplier.
“We have nothing to worry about if the weather stays like this,” said Joanna Gres, a ballet dancer with a troupe attached to the Polish military.
Bulgaria, too, has sufficient gas supplies for the next month, Alexander Nikolov, the energy minister, told Bulgarian news media, vowing that the country would “not negotiate under pressure and with its head bowed. ”
A top German official said the flow of Russian gas to Germany, Russia’s biggest energy customer, remained steady, while adding that the country could live off existing reserves until at least next winter.
Russia announced the cutoff a day after 40 U.S.-led allies met at the Ramstein Air Base in Germany and pledged to provide Ukraine with long-term military aid, following a weekend visit to the country by top Biden administration officials who said they want to see Russia not only defeated but degraded militarily.
That toughened American message is viewed by Mr. Putin and his subordinates as validation of their argument that the Ukraine war is really about the American desire to weaken Russia, and they are indirectly at war with NATO.
Despite fears of a broadened war, there was also a small measure of cooperation on Wednesday between Russia and the United States, which announced a prisoner swap.
They confirmed that Trevor R. Reed, a former Marine convicted on charges that his family said were bogus, had been freed, an unexpected diplomatic success. Mr. Reed, first detained in 2019, was released in exchange for Konstantin Yaroshenko, a Russian pilot sentenced to a lengthy term in the United States on cocaine-trafficking charges.
Other Americans remain in detention in Russia, including Paul Whelan, who was sentenced in 2020 to 16 years in prison on espionage charges during a trial that was closed to the public; and Brittney Griner, a basketball star arrested in mid-February on drug charges that could carry a sentence of up to 10 years.
Neither the American nor Russian sides gave any indication that the exchange signaled a broader diplomatic effort to de-escalate the Ukraine crisis.
Ukraine appeared to have attempted to strike deeper into Russian territory overnight, although officials on both sides were vague about the details. Three local governors described drone flights and explosions as attacks.
Mykhailo Podolyak, a close adviser to President Volodymyr Zelensky of Ukraine, also described the explosions inside Russia as attacks on sites that Russia had used to launch the invasion, but he attributed them to “karma” — not the Ukrainian military.
As described by the three Russian governors and Russian media, an ammunition depot was set afire near Belgorod, a city less than 20 miles from the border, two explosions were reported in Voronezh, nearly 200 miles from the border, and a Ukrainian drone was shot down over Kursk, about 70 miles from the border. If Ukraine was responsible, the attacks in Kursk and Voronezh would be the deepest inside Russia since the Feb. 24 invasion.
In Moscow, Nikolai Patrushev, the secretary for Mr. Putin’s security council, urged Russian officials across a wide swath of the southwestern region near Ukraine to ensure emergency alerts and civil defense facilities were “working reliably.”
Ukraine’s Defense Ministry has generally declined to discuss reports of attacks on Russian soil. Ukrainian officials have, for example, declined to comment on Russia’s claim that two Ukrainian helicopters fired on an oil depot in Belgorod in early April. In more than two months of war, the fighting has largely been contained within Ukraine’s borders.
Over the past few weeks Russian forces have concentrated on a full-scale assault in eastern Ukraine’s Donbas region, where analysts say Russia is making slow and measured advances on the ground as it confronts entrenched Ukrainian troops.
The pace of Russia’s ground assault appears more planned and deliberate than the initial invasion in February, which aimed at seizing more Ukrainian territory and depended on swift advances of tanks — a strategy that failed, at great cost to Russian forces.
Military analysts with the Institute for the Study of War, a Washington research group, said in their Tuesday assessment that Russian forces had “adopted a sounder pattern of operational movement in eastern Ukraine,” which is allowing them to “bring more combat power to bear” in their narrower goal of capturing just the eastern region.
Ukrainian troops have been defending positions in Donbas region since 2014, when secessionists there, backed by Russia, declared themselves the Donetsk People’s Republic and Luhansk People’s Republic.
Matina Stevis-Gridneff reported from Brussels, Neil MacFarquhar from Istanbul, and Shashank Bengali and Megan Specia from London. Reporting was contributed by Andrew Higgins from Warsaw, Ivan Nechepurenko from Tbilisi, Georgia, Cora Engelbrechtfrom Krakow, Poland, Liz Aldermanfrom Paris, Jane Arraf from Lviv, Ukraine, Matthew Mpoke Bigg from London and Rick Gladstone from New York.