A technical failure at Europe's largest nuclear power plant in Ukraine has caused power cuts in parts of the southeast of the country and the Russian-annexed region of Crimea.
Ukraine's energy minister said on Wednesday that a technical fault had cut power production but he insisted the incident posed no danger.
Volodymyr Demchyshyn said the accident occurred in one of the six blocks at the Zaporizhzhya plant. The incident was "in no way" linked to power production, he told a news conference.
"There is no threat ... there are no problems with the reactors," said Demchyshyn, who took up his post in a new government only on Tuesday. He added that he expected the plant to return to normal operations on December 5.
"Its power output is not being used. I think the problem will be resolved by Friday."
The accident which took place on Friday, reportedly caused by a short circuit, has added to the country's already serious power shortage which was brought about by months of fighting between the government and Russian separatists.
The plant in the city of Enerhodar has six power-producing units and a 6,000-megawatt generating capacity, accounting for more than one-fifth of electricity production in Ukraine. The affected unit was put into commission in 1986.
State nuclear power station operator Energoatom said damage to a transformer in a power-generating unit provoked an automatic shutdown in the system.
The reactor in the unit has been put into cold shutdown, making chain reactions impossible, Energoatom said.
The plant's operator revealed earlier this week that a problem had occurred with a power-generating unit, but concern was provoked on Wednesday after Prime Minister Arseniy Yatsenyuk referred to an unspecified incident during a Cabinet meeting.
France's public nuclear safety institute IRSN said it had not detected any unusual radioactivity in Ukraine after Friday's accident and that it presented no danger to the nearby population or environment.
An explosion and fire at Ukraine's Chernobyl power plant in 1986, the world's worst nuclear accident, was caused by human error and a series of blasts sent a cloud of radioactive dust billowing across northern and Western Europe.