BRUSSELS — The leaders of three eastern members of the European Union said Tuesday that they had traveled to Kyiv on a high-risk mission that was kept under wraps until after they had boarded a train to the embattled Ukrainian capital.
Poland’s prime minister, Mateusz Morawiecki, posted photos on Facebook of the men sitting round a table and poring over maps, and the Czech prime minister, Petr Fiala, did the same on Twitter. It was unclear what the setting was.
“It is here, in war-torn Kyiv, that history is being made,” Mr. Morawiecki wrote. “It is here, that freedom fights against the world of tyranny. It is here that the future of us all hangs in the balance.”
In the photos, Mr. Morawiecki and Mr. Fiala are seated with the prime minister of Slovenia, Janez Jansa, and Jaroslaw Kaczynski, the deputy prime minister of Poland, who is leader of the right-wing Law and Justice Party.
The images sought to convey a daring show of support for Ukraine three weeks after Russian troops invaded the country, and as the mayor of Kyiv warned of growing danger for the capital and its inhabitants.
The symbolism was powerful.
The Czech and Polish people were subjugated by the former Soviet Union and lived through decades of communist rule. Now, alarm has been growing that President Vladimir V. Putin is seeking to turn back the clock more than 30 years and trying to reclaim the lost Soviet sphere of influence.
The European leaders were reported to have traveled by train from the Polish border, a journey of at least seven hours. Ukrainian officials released few details about the trip.
Ukraine’s prime minister, Denys Shmyhal, writing on Twitter on Tuesday afternoon, said that the three traveling prime ministers had arrived “on behalf of” the European Union Council. However, E.U. officials said the men had not received the European Union’s blessing for their trip.
The visit came as Russian troops stepped up their bombardment of the capital, striking a military factory near the center of Kyiv and residential buildings and civilian areas in the western and northern districts around 5 a.m. The strike on the military factory, which caused extensive damage to shops and buildings, was the first bombardment in downtown Kyiv in the three weeks since Russia invaded.
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The office of the Polish prime minister had earlier released a statement saying that the delegation would meet with President Volodymyr Zelensky of Ukraine and Mr. Shmyhal, the prime minister. The aim of the visit was to express the European Union’s “unequivocal support for sovereignty and independence of Ukraine,” said the statement.
The claims that the three leaders were representing the European Union created unusual friction within the bloc. The E.U.’s 27 member states have projected a united front against Moscow, taking extraordinary measures to punish it for the attack on Ukraine with record speed.
Prime Minister Morawiecki of Poland brought up his intention to visit Kyiv at an E.U. meeting last week at Versailles, outside Paris. But the visit to Kyiv never became a formal E.U. mission.
European diplomats said that the three leaders’ travels were part of a broader Eastern European effort to push the European Union to expand sanctions and offer more military help to Ukraine, as well as to fast-track E.U. membership for Ukraine. The majority of E.U. member nations are resisting those moves.
Still, the reported visit to Kyiv, which some E.U. officials worried might lead to promises that could not be kept, was welcomed as brave in parts of the bloc.
“This is Europe at its best,” declared a headline in the popular German tabloid Bild, on an article that said: “Putin’s war is not over as long as Europe is ready to defend its values. With all the means it takes to do so. Even if it’s just a train ride in the shadow of bombs and missiles.”