In a statement on social media, Energoatom said Russian forces on Monday "kidnapped" the head of information technology Oleg Kostyukov and the plant's assistant general director Oleg Osheka and "took them to an unknown destination".

Energoatom called on International Atomic Energy Agency (IAEA) chief Rafael Grossi "to make every effort" to secure their release.

Russian troops captured the Zaporizhzhia nuclear power plant at the beginning of March, in the early days of Russia's invasion of Ukraine.

Ukraine has recently accused Russia of detaining several of the plant's employees.

Last week Energoatom said Russia detained and mistreated the plant's deputy director general for human resources, Valeriy Martyniuk.

In a statement released late Tuesday the IAEA, which has experts at the nuclear site, announced that Martyniuk had been released.

Grossi welcomed his release while expressing "deep concern" at the two new detentions at the nuclear plant.

"This is another concerning development that I sincerely hope will be resolved swiftly," he said.

The IAEA statement said that Grossi was continuing consultations on securing a "nuclear safety and security protection zone" around the site.

In late September, the agency said Russia detained the chief of the power station, Ihor Murashov, for several days before releasing him on October 3.

The nuclear plant -- Europe's largest atomic facility -- is located in Russian-held territory of Ukraine's Zaporizhzhia region, which Moscow claims to have annexed together with three other territories in Ukraine: Donetsk, Lugansk and Kherson.

Moscow and Kyiv have traded blame for months over shelling near the Russian-held facility, sparking fears of a nuclear disaster and spurring calls to de-militarise areas around atomic facilities in Ukraine.