High Representative of the European Union Josep Borrell and Croatian Prime Minister Andrew Plenkovic during a Special meeting of the European Council in light of Russia's aggression against Ukraine, in Brussels, Belgium, 24 February 2022. Olivier Hoslet
High Representative of the European Union Josep Borrell and Croatian Prime Minister Andrew Plenkovic during a Special meeting of the European Council in light of Russia's aggression against Ukraine, in Brussels, Belgium, 24 February 2022. Olivier Hoslet/Pool via REUTERS. Reuters / POOL

An international peacekeeping mission should be sent to Ukraine and be given the means to defend itself, the leader of Poland's ruling party said on Tuesday after meeting Ukrainian President Volodymyr Zelenskiy.

Jaroslaw Kaczynski made his remarks after he and the prime ministers of the Czech Republic, Poland and Slovenia arrived in Kyiv in a show of high-level backing for Zelenskiy, who briefed them on the war with Russia.

"I think that it is necessary to have a peace mission - NATO, possibly some wider international structure - but a mission that will be able to defend itself, which will operate on Ukrainian territory," Kaczynski told a news conference.

"It will be a mission that will strive for peace, to give humanitarian aid, but at the same time it will also be protected by appropriate forces, armed forces," said Kaczynski, who is seen as the main decision-maker in Poland.

Russian air strikes and shelling hit Kyiv on Tuesday, killing at least five people, authorities said, as invading forces tightened their grip and the mayor announced a 35-hour curfew.

Polish Prime Minister Mateusz Morawiecki, Czech counterpart Petr Fiala and Slovenia's Janez Jansa, who all travelled by train, were the first foreign leaders to visit the capital since the invasion last month.

Zelenskiy, noting that many ambassadors had left Kyiv, said the visiting leaders were "not afraid of anything and are more afraid of our fate" and thanked them for their support.

"We absolutely trust these countries and the leaders of these countries... we are 100% sure that everything we discuss will achieve its goals for our country, our security and our future," he told the news conference.

The Czech Republic and Poland, former communist countries that are members of both the EU and NATO, have been among the strongest backers of Ukraine in Europe since the Russian invasion.

Before the meeting, Morawiecki tweeted that "it is here, in war-torn Kyiv, that history is being made. It is here, that freedom fights against the world of tyranny. It is here that the future of us all hangs in the balance".

The idea of the trip was agreed at an EU leaders' summit in Versailles in France last week, Polish prime ministerial aide Michal Dworczyk said.

But an EU official said there was no "formal mandate" extended by Brussels.

Russia calls its actions a "special military operation" to "denazify" Ukraine, which Kyiv and its Western allies reject as a pretext for an unjustified and illegal attack.