A minor accident occurred at the Zaporozhskaya nuclear plant last Friday, according to the facility’s website. A reactor was switched off and maintenance was carried out as a result.

The incident was not made public until Wednesday, when PM Yatsenyuk asked the energy minister to report on what happened and how the ministry is handling the situation.

Ukraine's energy minister, Vladimir Demchyshyn, said that the accident posed no risk.

"There is no threat ... there are no problems with the reactors," Demchyshyn said at briefing, adding the accident affected the power output system and "in no way" was linked to power production itself.

Demchyshyn said that the reactor would be restarted December 5.

The accident left several dozen towns and villages without electricity, Russian media reported, citing local officials.

Four more reactors at the plant remain operational, according to the facility’s website. One is undergoing planned repairs.

Zaporozhskaya first reactor came on line in November 1984. Within the course of the next 10 years, five more reactors were brought into operation. The plant currently produces one-fifth of Ukraine’s electricity.

The Vienna-based International Atomic Energy Agency (IAEA) told Reuters it had no comment to make on the Zaporoshskaya accident so far.

An international convention, adopted after the 1986 Chernobyl disaster, obliges countries to notify the IAEA of any nuclear accident that can affect other countries.