In Moscow, Russia's foreign ministry said Russia was doing everything to ensure an IAEA visit to the plant could take place safely.
Ukraine's President, Volodymyr Zelenskiy has 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.
According to Reuters, Zelensky 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 organisations 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.
In Moscow, Russia's foreign ministry said Russia was doing everything to ensure an IAEA visit to the plant could take place safely. Ministry spokesperson Maria Zakharova said Ukraine was trying to disrupt such a visit by attacking the plant.
Residents in Zaporozhzhia city, 50 km northeast of the plant, 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 was fully disconnected on Thursday.
Vladimir Rogov, a Russian-appointed official in the occupied town of Enerhodar near the plant, blamed Ukrainian armed forces for Thursday's incident, saying they caused a fire in a forest near the plant.
"This was caused by the disconnection of power lines from the Zaporizhzhia nuclear power station as a result of provocations by Zelenskiy's fighters," Rogov wrote on Telegram. "The disconnection itself was triggered by a fire and short circuit on the power lines."
Russia’s Defence Ministry said on Friday that its forces had destroyed a US-made M777 howitzer which it said Ukraine had used to shell the Zaporizhzhia plant.
Satellite images showed a fire near the plant but Reuters could not verify its cause.