Russia accused Ukraine on Saturday of planning to attack a nuclear plant in the Kursk region that President Volodymyr Zelenskiy's troops have entered and blame such a "provocation" on Moscow, Interfax news agency said.

Kyiv denied that as "insane" propaganda.

Ukraine launched an incursion into Russia's western Kursk region on August 6 to try and swing the dynamics of the two-and-a-half year war in its favour after Moscow's 2022 invasion.

Russia's defence ministry said there would be a harsh response to any attack on the Kursk power plant, which remains under its control, Interfax reported. It gave no evidence for its accusation against Ukraine, but said a large surrounding area could be contaminated by an attack.

"We are seeing another surge in insane Russian propaganda about alleged Ukrainian plans to use 'dirty bombs' or attack nuclear plants. We officially refute these false claims," said Ukrainian Foreign Ministry spokesperson Heorhii Tykhyi on X.

"Ukraine has no intention or ability to take any such actions."

Russian state nuclear firm Rosatom, which also runs the Zaporizhzhia plant in Ukraine controlled by Russia, also accused Kyiv of threatening both plants' security, RIA news agency said, without offering any evidence.

Rosatom head Alexei Likhachev discussed the situation with International Atomic Energy Agency (IAEA) head Rafael Grossi by phone and invited him to visit the Kursk plant, RIA added.

Russia and Ukraine have repeatedly accused each other of trying to sabotage the operation of the Zaporizhzhia plant, Europe’s biggest, in southeastern Ukraine.

It is shut down but needs external power to keep its nuclear material cool and prevent a meltdown.