The Zaporizhzhia NPP site was the scene of a battle between Russian and Ukrainian forces as the former advanced towards the city of Zaporizhzhia.
A fire broke out at the plant, which has since been extinguished. No radiation leak has been detected by the Ukrainian nuclear regulator.
"The Zaporizhzhia NPP site has been seized by the military forces of the Russian Federation," a statement from the State Nuclear Regulatory Inspectorate of Ukraine read. "The fire was extinguished by the Ukrainian State Emergency Service units. Information on the dead and injured is absent."
The plant is responsible for a fifth of Ukraine's electricity.
The latest disturbing development was denounced by NATO chief Jens Stoltenberg.
"Overnight we have seen reports about the attack against the nuclear power plant," he said. "This just demonstrates the recklessness of this war and the importance of ending it and the importance of Russia withdrawing all its troops and engaging good faith in diplomatic efforts."
Ireland's Minister for Foreign Affairs Simon Coveney called the attack "utterly reckless."
"Russia’s attack on the Zaporizhzhia nuclear power station is utterly reckless," he wrote on Twitter. "Russia’s military activity in the area must cease immediately. This is a grave threat to the European continent."
Ukrainian President Volodymyr Zelensky repeated his plea for the country's European allies to take military action against Russia.
"If there is an explosion, it is the end of everything," he said. "The end of Europe. Only immediate European action can stop Russian troops."
