Ukraine has halted the transportation of Russian gas supplies through the country after a prewar transit deal expired at the end of last year, the nation’s energy minister confirmed.

Minister of Energy of Ukraine Herman Halushchenko said Wednesday morning on the Telegram messaging app that the transit was stopped “in the interests of national security.”

“This is a historic event. Russia is losing markets and will incur financial losses. Europe has already decided to phase out Russian gas, and (this) aligns with what Ukraine has done today,” Halushchenko said, according to a translation by The Associated Press.

Russia’s Gazprom said in a statement that Kyiv’s refusal to extend the deal means the majority state-owned energy corporation has “no technical or legal possibility” of sending gas through Ukraine. Transportation stopped at 8 a.m. Moscow time, Gazprom said.

Even as Russia’s war against Ukraine began in 2022, Russian natural gas flowed through the country’s pipeline network, established when both nations were part of the Soviet Union, to Europe under a five-year deal. Ukraine collected transit fees, while Gazprom earned money from the gas.

Nearly 40 percent of the European Union’s pipeline natural gas was supplied by Russia before the war. When the fighting got underway, an energy crisis in Europe followed since Russia cut off most supplies through other pipelines. Europe has since outlined plans to completely eliminate Russian gas imports by 2027.

The Associated Press contributed.