Zaporizhzhia, Ukraine — Ukrainian President Volodymyr Zelenskyy has claimed that Russia is plotting a potentially dangerous attack on Europe's largest nuclear power plant, which Russian forces have occupied for more than a year. Russia has accused Ukraine, meanwhile, of plotting to attack the same sprawling Zaporizhzhia Nuclear Power Plant in Enerhodar, southern Ukraine, in the next two days. 

It was a nerve-racking night for people across Ukraine amid the crossfire of accusations, but especially in the towns and cities near the Zaporizhzhia plant, including the city of Zaporizhzhia just a few miles away, which Russia never managed to capture.

Zelenskyy laid out his claims in detail Tuesday night, saying Russian forces had "placed objects resembling explosives on the roof of several power units" at the power plant.

Russia, meanwhile, accused Ukraine of planning to strike the plant with missiles or drones packed with radioactive waste from other nuclear facilities.

Neither side has provided any evidence to back up its claims.

The Zaporizhzhia plant has been under Russian control since it was captured just a month after Vladimir Putin launched his full-scale invasion of Ukraine in February 2022. The sprawling compound has been fought over ever since, with rocket strikes — blamed by either side on the other — repeatedly severing its vital connection to Ukraine's national electricity grid.

Fears of a catastrophe spiked in early June when Ukraine accused Russia of blowing up a major dam upstream of the plant, dropping water levels in a reservoir used to provide cooling water to the Zaporizhzhia facility.

The head of the U.N.'s nuclear watchdog agency has visited the plant multiple times, including right after the dam explosion, and described the situation there as "serious," but not an immediate safety threat — unless the cooling pond at the compound, or any other part of it, comes under new attack.

International Atomic Energy Agency (IAEA) experts at the Zaporizhzhia plant have in recent days inspected parts of the facility, including some sections of the perimeter of the cooling pond, and have also conducted regular tours of the site without observing any apparent indications of mines or explosives, Director General Rafael Mariano Grossi said Wednesday.

Grossi said the IAEA team had requested additional access to look for mines or explosives at the site following the claims made this week, in particular access to the rooftops of reactor units 3 and 4, as mentioned by Zelenskyy, and parts of the turbine halls and some parts of the cooling system at the plant. 

"With military tension and activities increasing in the region where this major nuclear power plant is located, our experts must be able to verify the facts on the ground," Grossi said. "Their independent and objective reporting would help clarify the current situation at the site, which is crucial at a time like this with unconfirmed allegations and counter allegations."

Regional sources told CBS News on Wednesday that IAEA inspectors have been kept out of key sites at the nuclear facility by the Russian forces who control it.   

Authorities routinely run emergency drills in the region for civilians to practice what to do in the case of a major incident.

A Ukrainian government official told CBS News on Wednesday that residents would receive a warning on their phones in the event of an incident instructing them to either remain inside and close all doors and windows, or to get ready to evacuate.

CBS News' Christina Ruffini in Washington D.C. contributed to this report.

In:
• War
• Nuclear Power Plant
• Ukraine
• Russia
• Vladimir Putin