The prime ministers, who arrived by train, sat round a table with their Ukrainian counterpart Denis Shmyhal amd and the Ukrainian president.
The Polish, Czech and Slovenian prime ministers met Ukrainian President Volodymyr Zelensky in Kyiv on Tuesday in the first visit by foreign leaders to Ukraine's besieged capital since Russia's invasion.
The prime ministers, who arrived by train, sat round a table with their Ukrainian counterpart Denis Shmyhal amd and the Ukrainian president, who detailed the situation to them.
"They are shelling everywhere. Not only Kyiv but also the western areas," Zelensky told them in comments translated into English, a video posted on his Telegram account showed.
"We have to halt this tragedy unfolding in the East as quickly as possible," Polish Prime Minister Mateusz Morawiecki said in a post on Facebook
announcing their arrival.
Ukraine had the "unequivocal support" of the European Union, he added.
Shmyhal earlier confirmed their arrival in a post on Twitter, saluting "the courage of true friends of Ukraine".
He said their talks would focus on support for Ukraine and "strengthening sanctions against the Russian aggression".
Morawiecki, Czech premier Petr Fiala and Slovenia's Prime Minister Janez Jansa, are visiting as "representatives" of the European Union, said an early statement from the Polish government.
The visit comes as Russia pummels targets across Ukraine including Kyiv, which has nearly been encircled by Moscow's troops, and as Russia and Ukraine are due to resume talks to end the nearly three-week war.
"In such crucial times for the world, it is our duty to be in the place where history is being made," Morawiecki said in a Facebook
post earlier Tuesday.
"Because this is not about us, it is about the future of our children who deserve to live in a world free from tyranny," he said.
The government statement said that the visit had been organised "in agreement" with European Council chief Charles Michel and European Commission president Ursula von der Leyen.
"The purpose of the visit is to confirm the unequivocal support of the entire European Union for the sovereignty and independence of Ukraine and to present a broad package of support for the Ukrainian state and society," the statement said.
The trio is accompanied by Jaroslaw Kaczynski, leader of Poland's populist right-wing Law and Justice (PiS) party.