His dramatic call for help came as Russian forces were approaching the Ukrainian capital, with some units reportedly reaching the city's northern suburbs.

"If you have combat experience in Europe and do not want to look at the indecision of politicians, you can come to our country and join us in defending Europe, where it is very necessary now," Zelensky, who appeared tired, said in a video.

Speaking on the second day of the attack launched by Russian President Vladimir Putin, Zelensky also asked Europeans to "demand from your governments that Ukraine receive more financial, more military aid."

The 44-year-old leader also said the West was in no hurry to help Ukraine against the Russian invasion.

"How are you going to defend yourself when you are so slowly helping us in Ukraine?," he said.

"State institutions in Europe are not in a hurry with really strong decisions."

Western countries have imposed sanctions on Moscow, but stopped short of cutting Russia off from the SWIFT international payments system.

Zelensky demanded that Europe go further and "act without delay."

"Europe has enough strength to stop this aggression," he said.

"Cancellation of visas for Russians? Disconnect from SWIFT? Complete isolation of Russia? Recall of ambassadors? Oil embargo? Closing the sky? Today, all this must be on the table," he said.

The EU has said it could impose more sanctions on Russia in the future.

Ukraine said Russian forces were approaching Kyiv from the north and from the east on Friday.

Putin launched the attack on Ukraine in the early hours of Thursday.