Any attempt to disconnect Ukraine's Zaporizhzhia Nuclear Power Plant (ZNPP) and divert it to Russian-occupied areas is "unacceptable," the State Department said Thursday.

The plant remains under Russia's control after Moscow's forces seized it and the surrounding area in March. The facility had continued to feed power to Ukraine's national power grid but the country’s energy operator said Thursday that the plant had been disconnected after fire damaged power lines connecting it to the national grid.

State Department spokesman Vedant Patel said the US is "closely monitoring" reports that the last two operational reactors had been shut down and charged Russia with seeking to further undermine Europe's energy security.

"It is clear that Russia's shelling and seizure of Ukraine's power plants and infrastructure are part of its strategy to create energy crises in Europe," he told reporters on a conference call.

Pro-Russian authorities in Energodar, where the power plant is located, said the security system was activated at the plant because of a power outage following conflicts in the region.

The Zaporizhzhia plant in southeast Ukraine is the largest nuclear power plant in Europe. The plant has six nuclear reactors and an electricity generation capacity of 5,700 megawatt-hours. It provides 20% of the total electricity in Ukraine.

Artillery strikes have been taking place around the power plant in recent weeks with Ukraine and Moscow accusing each other of carrying out the attacks.