Zelensky said this week that Russian forces controlling Zaporizhzhia -- Europe's biggest nuclear plant -- were planning a "terror attack" by orchestrating a radiation leak.

The Kremlin said it was a "lie" but the president's warning put many Ukrainians on alert with demand for iodine at many pharmacies sky rocketing.

"Read and share but don't panic! Don't play the enemy's game. President Zelensky said nothing new. Russia is a terrorist country from which, like a monkey with a grenade, you can expect anything," the Ukrainian health ministry said.

In a separate statement Friday, it warned against the adverse implications of incorrectly administering iodine, warning it could even be fatal.

"The uncontrolled intake of potassium iodide is dangerous," it said.

Fears for the nuclear power plant have persisted throughout Moscow's Ukraine offensive and have increased after the destruction of a dam that provided the plant with cooling water.

UN nuclear chief Rafael Grossi is expected to arrive later Friday in the Russian region of Kaliningrad to meet with the head of Russia's nuclear agency.