Firefighters cannot get near the flames because they are being shot at, he said, and Ukrainian Foreign Minister Dmytro Kuleba tweeted a plea to the Russians to stop the assault and allow fire teams inside.
"We demand that they stop the heavy weapons fire," Mr Tuz said in a video statement.
"There is a real threat of nuclear danger in the biggest atomic energy station in Europe."
The assault renewed fears that the invasion could damage one of Ukraine's 15 nuclear reactors and trigger another emergency like the 1986 Chernobyl accident, the world's worst nuclear disaster.
