The Prime Minister of the United Kingdom Boris Johnson met with Ukrainian President Volodymyr Zelenskyy during a visit to Kyiv on Saturday, an aide to the Ukrainian leader said.

"Boris Johnson's visit in Kyiv began just now with a tete-a-tete meeting with President Zelenskyy," presidential aide Andriy Sybiha said on Facebook, posting a photo of the pair.

The photograph showed the pair sitting opposite each other in a grand room. Johnson was wearing a dark suit and Zelensky a khaki overall, his signature attire in public appearances since Russia invaded Ukraine end of February.

"The UK is the leader in the defense support of Ukraine," Sybiha wrote.

Sybiha described Johnson as "the leader of the anti-war coalition. The leader of sanctions on the Russian aggressor."

Johnson's visit to the Ukrainian capital followed trips to Kyiv of European Commission President Ursula von der Leyen and the EU's foreign policy chief Josep Borrell on Friday and the visit of the Austrian Chancellor Karl Nehammer earlier on Saturday.

Johnson's Downing Street office said he was in Ukraine for a "show of solidarity" with the country's people.

The European visits come after Ukraine rebuffed Russian troops from the Kyiv region late last month.