Russian gas has stopped flowing to Europe via Ukraine, ending a major energy route that goes back to Soviet times and had even survived three years of full-scale war between the two states.

Ukraine cut off the transit route after an agreement signed in 2019 expired in the early hours of New Year’s Day, marking a new milestone in Europe weaning itself off Russian gas supplies over the past few years, and prompting immediate power cuts for hundreds of thousand of people in a breakaway region of Moldova.

Russia’s Gazprom said in a statement that it had stopped sending gas via Ukraine as of 8am Moscow time (5am GMT) on Wednesday. Ukraine’s energy minister, German Galushchenko, called the move “historic”, while the president, Volodymyr Zelenskyy, described it in a post on social media as “one of Moscow’s biggest defeats”.

Zelenskyy wrote: “When [Vladimir] Putin was given power in Russia more than 25 years ago, the annual gas pumping through Ukraine to Europe was 130+ billion cubic metres. Today, the transit of Russian gas is 0.”

The move prompted angry words from Slovakia’s prime minister, Robert Fico, who had lobbied against the decision in recent months. “Halting gas transit via Ukraine will have a drastic impact on us all in the EU but not on the Russian Federation,” he wrote on Facebook.

Elsewhere, however, there was celebration over a further step away from Russian energy dependency. Poland’s foreign minister, Radosław Sikorski, called the development “a new victory” for Europe.

The most immediate effect of the move came in the breakaway Moldovan region of Transnistria, which lost heating and hot water on Wednesday morning.

A statement on the website of Tirasteploenergo, the local energy company, said the heating cuts took effect at 7am local time (5am GMT) on Wednesday. It urged residents to dress warmly, gather family members together in a single room, hang blankets or thick curtains over windows and balcony doors, and use electric heaters.

“It is forbidden to use gas or electric stoves to heat the apartment. This can lead to tragedy,” the company said. One of its employees told Reuters by phone she did not know how long the situation would last.

Russian gas has flowed through Ukraine for decades, mainly via a Soviet-built pipeline that begins in Sudzha, a town in Russia’s Kursk region currently under the control of Ukrainian forces, and ends near Uzhhorod, on Ukraine’s western border with Slovakia.

The route was often fraught, with Russia accused of using gas flow for political blackmail over the years as its relations with Ukraine went through various crises.

A report published last month by the Center for European Policy Analysis (Cepa) claimed: “Russia has abused Ukraine and Europe’s dependence on gas supplies and transit revenues to extort political concessions, spread corruption and exert malign influence.”

Since Russia’s invasion of Ukraine in February 2022, the share of Russian gas on the European market has dropped from about 35% to about 8%, as European countries sought to diversify supplies.

The Nord Stream undersea pipeline, which linked Russia and Germany without the need for transit countries, was destroyed in September 2022, with reports suggesting a Ukrainian team was behind the attack.

But Slovakia, Hungary and Austria still rely on Russian gas, and even as war has raged in Ukraine over the past three years, the transit continued.

The gas provided revenue for both Russia and Ukraine, including hundreds of millions of euros a year in transit fees for Kyiv.

Negotiations took place last year to extend the deal, with various options suggested including a scheme for Russia and Azerbaijan to sell each other gas and brand the transit gas as Azerbaijani gas. These options were rejected by Ukraine, however, as the government decided the benefits of ending transit would outweigh the costs.

“We won’t allow them to earn additional billions off our blood,” said Zelenskyy last month. He said the only option Ukraine would consider would be if consumers deferred payment to Russia until after the end of the war, but this was never likely to be an acceptable solution for Gazprom or the Kremlin.

The only Russian gas route to Europe still in operation is TurkStream, a Black Sea pipeline that sends gas to Hungary and Serbia. According to analysts, as the Ukraine transit gas only accounted for about 5% of Europe’s gas needs, it is likely that alternative sources can be found for EU countries to make up the deficit without a significant impact on prices.

Nonetheless, the Russia-friendly leaders of Slovakia and Hungary, Fico and Viktor Orbán, have criticised the move. Slovakia has estimated that the loss of supplies through Ukraine could cost about €150m (£125m) in increased fees.

Fico travelled to Moscow last month for discussions with Putin, a rare visit for an EU leader since the start of the war. On his return, he threatened that if Ukraine did cut off Russian gas flows, Slovakia would consider cutting electricity supplies to Ukraine, which has had to resort to imports as Russia continues a targeted bombing campaign against the country’s energy infrastructure.

“We are fighting for lives; Fico is fighting for money,” said a furious Zelenskyy in response to the threat. “To be honest, during war it’s a bit shameful to talk about money, because we’re losing people,” he added.

Moldova faces perhaps the most difficult consequences of any European country from the end of Ukraine’s gas transit. In December, it declared a state of emergency, fearing the cut-off would affect its main electricity source, a gas-powered generating plant in Transnistria.

A referendum on EU accession in Moldova passed last year with a razor-thin majority and Russia has been accused of meddling in the electoral system. Gazprom had threatened to stop deliveries to Moldova even if a deal was done to keep the Ukraine transit going, citing a dispute over unpaid bills. On Wednesday the Moldovan government accused Moscow of “blackmail”.

However, most of Moldova’s population of 2.5 million are able to make up for the loss of Russian gas by using reserves and importing from Romania, while Transnistria, the pro-Russia breakaway region that is home to about 450,000 people, is likely to be hit hardest.

The Moldovan government spokesperson Daniel Vodă said on Wednesday that the central authorities were “looking for alternative solutions to provide [Transnistria residents] with heat and energy”.