Europe's Nuclear Power Plant: Why Word Presidents Must Act Fast - Ukrainian President

Ukraine's president urged the world to act much faster to force Russian troops to vacate Europe's largest nuclear power plant after the site was cut from electricity for hours in an incident he said risked an international radiation disaster.

President Volodymyr Zelenskiy said Russian shelling on Thursday had sparked fires in the ash pits of a nearby coal power station that disconnected the Zaporozhzhia plant from the power grid. A Russian official said Ukraine was to blame.

Back-up diesel generators ensured power supply vital for cooling and safety systems at the plant, Zelenskiy said, praising the Ukrainian technicians who operate the plant under the gaze of the Russian military.

"The key thing is...international pressure is needed that will force the occupiers to immediately withdraw from the territory of the Zaporizhzhia nuclear power plant," he said in a video address on Thursday evening.

"The IAEA and other international organizations must act much faster than they're acting now. Because every minute the Russian troops stay at the nuclear power plant is a risk of a global radiation disaster," he said, referring to the United Nations nuclear watchdog.

Residents in Zaporozhzhia city, 50 km northeast of the plant and some 435 km (270 miles) to the southeast of Kyiv, expressed alarm at the situation.

"Of course I am scared. Everyone is scared, we don’t know what will happen next, what is waiting for us every next minute, second," said social media manager, Maria Varakina, 25.

School teacher Hanna Kuz, 46, said people were afraid that the Ukrainian authorities might not be able to warn residents in time in case of radiation fallout.

Ukraine's state nuclear company Energoatom said one of the plant's two functioning reactors had been reconnected to the grid and was again supplying electricity after it fully disconnected on Thursday.