He begged world leaders to wake up and prevent Europe from "dying from a nuclear disaster" after the continent's largest plant caught fire after it was shelled.

"No country other than Russia has ever fired on nuclear power units," he said in a video message released by his office. "This is the first time in our history. In the history of mankind. The terrorist state now resorted to nuclear terror."

The station at Zaporizhzhia, an industrial city in the southeast, supplies an estimated 40 percent of the country's nuclear power and, according to Zelensky, houses six of Ukraine's 15 reactors.

According to Kyiv, the blaze started after Russian troops fired on the facility.

"These are tanks equipped with thermal imagers, so they know where they are shooting," said Zelensky.

But "essential" equipment at the station was unaffected and radiation levels were normal, local officials told the UN's atomic watchdog.

Ukraine's nuclear facilities have been a main point of concern after Russia's military invaded the country last week and began bombarding cities with shells and missiles.

"If there is an explosion, it is the end of everything. The end of Europe," Zelensky said. "Only immediate European action can stop Russian troops."