Ukraine’s national grid operator said the Zaporizhzhia nuclear power station was reconnected to the grid on Thursday, easing fears of a disaster after electricity to the plant was lost during Russian air strikes.

Back-up diesel generators — a last line of defence to prevent a meltdown from overheating reactor fuel — kicked in after external power was lost to the plant early on Thursday, but they have only enough fuel to power it for 10 days. Ukraine blamed Russia for the loss of power to the plant in southeastern Ukraine. Officials in the part of the Zaporizhzhia region called it a “provocation” by Kyiv.

The incident renewed fears of an accident at Europe’s largest atomic power station, nearly four decades after the Chornobyl nuclear disaster, but national grid operator Ukrenergo said repairs had been carried out quickly.

“Specialists of ‘Ukrenergo’ have restored the power supply of the Zaporizhzhia NPP (nuclear power plant), which was interrupted by today’s missile strikes,” it said. “The ZNPP is switching from diesel generators to receiving electricity for its own needs from the unified energy system of Ukraine.”