The plant -- Europe's largest facility -- was cut off from Ukraine's power network for the first time in its history on Thursday due to "actions of the invaders", Energoatom said.

Early Friday, the operator said on Telegram that all reactors remain "disconnected from the electrical grid" as of 9:00 am local time (0600 GMT).

However, a severed power line -- the cause of the outage -- has been "restored" and "work is ongoing to prepare the connection" of two of the plant's six reactors.

Zaporizhzhia has been cause for mounting concern since it was seized by Russian troops in the opening weeks of the war.

In recent weeks, Kyiv and Moscow have traded blame for rocket strikes in the vicinity of the facility.

Ukrainian President Volodymyr Zelensky said late Thursday the cut-off was caused by Russian shelling of the last active power line linking the plant to the network.

"Russia has put Ukrainians as well as all Europeans one step away from radiation disaster," he said in his nightly address.

Kyiv suspects Moscow intends to divert power from the Zaporizhzhia plant to the Crimean peninsula, annexed by Russian troops in 2014.

On Thursday, Washington issued a direct warning against any such move.

"The electricity that it produces rightly belongs to Ukraine," State Department spokesman Vedant Patel told reporters.

"Any attempt to disconnect the plant from the Ukrainian power grid and redirect to occupied areas is unacceptable."