"Recently I received yet another alarming report from our intelligence. Now Putin does seem to be planning attacks on our nuclear power plants and the infrastructure, aiming to disconnect the plants from the power grid," Zelensky told the UN General Assembly.

Zelensky, delivering his speech in English, said that Russia was using satellites to gather images and detailed information about Ukraine's nuclear infrastructure.

"Any critical incident in the energy system could lead to a nuclear disaster, a day like that must never come," Zelensky said.

"Moscow needs to understand this, and this depends in part on your determination to put pressure on the aggressor," he said.

"These are nuclear power plants. They must be safe."