External power must be restored to the Soviet-built Zaporizhzhia nuclear power plant in southern Ukraine, which is currently being cooled by emergency diesel generators after an external line was severed during fighting, Russia said on Wednesday. 

Heavy fighting, including drone and artillery strikes near several Soviet-era nuclear power stations in Ukraine, has repeatedly drawn grave warnings from the International Atomic Energy Agency (IAEA) over the risk of a major nuclear accident. 

"The situation at the station is under control," said Yevgeniya Yashina, a spokeswoman for the plant, adding that the staff were trained to respond and that radiation levels were normal.  

Russia's state news agency RIA quoted the plant's Russian-installed management as saying that backup electricity supply was sufficient for now, but that resuming regular electricity supply via the Dneprovskaya line was impossible due to Ukrainian shelling. 

Ukraine, in turn, has accused Russia of preventing repairs.

The Kremlin said that it was unreasonable for Ukraine to accuse Moscow of shelling the facility, given that Moscow controls the site. 

Power is needed to circulate water to cool the reactors and spent fuel, the IAEA said. 

"Europe's largest nuclear power plant has been without external power for more than a week now, which is by far the longest lasting such event during more than three and a half years of war," IAEA Director General Rafael Grossi said. 

The Zaporizhzhia plant has six Soviet-designed VVER-1000 V-320 water-cooled and water-moderated reactors containing Uranium 235. All reactors are currently shut down, but without any power - either external or supplied by the emergency generators - nuclear fuel could heat up, risking a meltdown. 

"The current status of the reactor units and spent fuel is stable as long as the emergency diesel generators are able to provide sufficient power to maintain essential safety-related functions and cooling," Grossi said. "It is extremely important that offsite power is restored." 

(With input from Reuters)