The three leaders went ahead with the hours-long train trip despite worries within the European Union about the security risks of traveling within a war zone.?

Poland's Prime Minister Mateusz Morawiecki said on Facebook in the evening that he, deputy Prime Minister Jaroslaw Kaczynski and the Czech and Slovenian leaders were in Kyiv.

Because of Russia's war on Ukraine the “world has lost its sense of security and innocent people are being killed and losing all their possessions,” Morawiecki said.?

“We must stop this tragedy ... this is why we are .. in Kyiv,” he said.?

It was a strong symbol of support for Ukraine while the long journey over land from Poland to Kyiv sent another signal, too: that most of Ukraine still remains in Ukrainian hands.

Poland's leaders, together with Prime Ministers Petr Fiala of the Czech Republic and Janez Jansa of Slovenia, said they were on an EU mission. But officials from the 27-nation bloc insisted that the trio had undertaken the trip independently.

The three Central European nations are former communist bloc countries that now belong to both the EU and NATO. Underlining the deteriorating security situation in Kyiv, a series of strikes hit a residential neighbourhood in the city again on Tuesday.

Jansa described the visit as a way to send a message that Ukraine is a European country that deserves to be accepted one day into the EU. In fact, the trip by the three prime ministers comes two weeks after Ukrainian President Volodymyr Zelenskyy made an emotional appeal to the European Parliament.

“We are fighting also to be equal members of Europe," Zelenskyy told EU lawmakers on March 1. "I believe that today we are showing everybody that is what we are.”

Jansa said the war has woken Europeans up to idea that the bloc represents fundamental ideas that are under threat — and which Ukrainians are defending with their lives.

"Thank you for not only defending your homeland and Europe as a territory, but for defending the very core of European values and our way of life. Your fight is our fight and together we will prevail,” he tweeted.

Jansa is a right-wing populist friendly with Hungarian Prime Minister Viktor Orban. The Slovenian prime minister has supported the false claims of former U.S. President Donald Trump that the 2020 U.S. election was rigged.

Jansa, 63, served as defense minister during the small state's brief and successful uprising against the Yugoslav army when Slovenia declared independence in 1991. Lately, he has been comparing Ukraine's resistance to Russia to Slovenia's uprising against a much stronger enemy.

Also traveling with the three leaders was Kaczynski, Poland's de-facto leader whose presence carries a certain symbolic significance.?

He is the surviving twin of the late President Lech Kaczynski, who died in a plane crash on Russian soil in 2010 along with 95 other Poles, among them political and military leaders, as they traveled to commemorate Poles executed by the Soviet secret police during World War II.

A Polish investigation determined that the crash was an accident caused by fog and pilot error. Still, Kaczynski, 72, has long suspected that Russian President Vladimir Putin had a role in provoking the accident, a suspicion that has not been proven.

“The aim of the visit is to express the European Union's unequivocal support for Ukraine and its freedom and independence," said Fiala, a conservative whose win in a parliamentary election last fall unseated populist billionaire Andrej Babis.

Morawiecki said on Facebook that the visit was agreed by the EU and that the United Nations was also informed.

“In such critical times for the world, it is our duty to be where history is forged,” Morawiecki said. “Because it's not about us, but about the future of our children, who deserve to live in a world free from tyranny.”

In Brussels, officials said they had been informed of the visit but characterized it as one taken independently into a war zone.

NATO Secretary-General Jens Stoltenberg, who was asked about the visit, didn't endorse it outright but said “I think it is important that leaders of NATO countries, of European member states, are engaging closely with President Zelenskyy.”

?The visit had been planned for several days but was kept secret for security reasons, said Michal Dworczyk, chief of staff for Morawiecki, adding that a proposal of concrete help for Ukraine would be presented to Ukraine's leaders.

Shortly before dawn and hours before the leaders were due in Kyiv, large explosions thundered across the city from what Ukrainian authorities said were Russian artillery strikes. The shelling ignited a huge fire and a frantic rescue effort in a 15-story apartment building. At least one person was killed and others remain trapped inside.

Shockwaves from an explosion also damaged the entry to a downtown subway station that has been used as a bomb shelter. City authorities tweeted an image of the blown-out facade, saying trains would no longer stop at the station.

Ahead of his departure, Morawiecki on Facebook recalled how the former Polish President Lech Kaczynski had made a visit to the capital of Georgia in 2008 when that ex-Soviet country was under attack from Russia.

He quoted President Kaczynski, who said at the time in Tbilisi: “Today Georgia, tomorrow Ukraine, the day after tomorrow the Baltic states, and then maybe it's time for my country, for Poland.”?