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 and sent demand for iodine at many pharmacies skyrocketing.

"Read and share but don't panic! Don't play the enemy's game. President Zelensky said nothing new," the Ukrainian health ministry said late on Thursday.

"Russia is a terrorist country from which, like a monkey with a grenade, you can expect anything."

In a separate statement on Friday, the ministry warned against the adverse effects of incorrectly administering iodine, adding that it could even be fatal.

Interior Minister Igor Klymenko said authorities were monitoring the situation.

"Specialists are ready for various scenarios," he said on social media.

An incident at the Zaporizhzhia nuclear plant could release radioactive iodine into the atmosphere and in turn increase the risk of thyroid cancer, as happened after the 1986 Chernobyl disaster.

The tablets can help prevent radioactive iodine from concentrating in the thyroid gland so it can be flushed out of the body naturally.

- 'Tired of being afraid' -

There were no signs of panic buying at Kyiv chemists on Friday but demand for the iodine tablets has soared.

Maria Dudar, a 21-year-old pharmacy employee, told AFP: "There is no panic but everyone is cautious."

Kyrylo Zalunin, a 37-year-old resident of Kyiv, said he saw the health ministry's recommendations but did not run to buy iodine.

"If you react to all these statements, you could lose your mind," he said.

Another resident of the capital, Oksana Zavgorodnia, said she was not afraid.

"We are tired of being afraid. We are hoping for the best," said the 52-year-old, as she and her husband left a chemist's shop.

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

UN nuclear chief Rafael Grossi met the head of Russia's nuclear agency Rosatom on Friday in Russia's European enclave of Kaliningrad, but there were no announced breakthroughs from the discussions.

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