"There is no threat... there are no problems with the reactors," Energy Minister Volodymyr Demchyshyn, who took up his post in a new government only on Tuesday, told a briefing.
Demchyshyn, said the accident which happened on Friday in one of the six blocs at Zaporizhzhya, Europe's largest nuclear powerplant, had been caused by a short circuit in the power outlet system and was "in no way" linked to power production.
In Vienna, the International Atomic Energy Agency said it had no immediate comment on the report.
Under an international convention, adopted after the April 1986 Chernobyl accident in what was then Soviet Ukraine, a country must notify the IAEA of any nuclear accident that can have an impact on other countries.
The explosion and fire at the Chernobyl power plant, 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.
Ukraine, Belarus and Russia, have estimated the death toll at only a few thousand as a result of the explosion while the environmental group Greenpeace says the accident will eventually cause up to 93,000 extra cancer deaths worldwide.
Interfax news agency said a 1,000-megawatt reactor was housed in the bloc at Zaporizhzhya where last Friday's accident occurred.
Demchyshyn said the affected bloc had been provisionally disconnected from the electro-energy system though its reactor continued to work normally.
"Its power output is not being used. I think that the problem will be resolved by Friday," he said.
The accident has had a slight impact on Ukraine's energy system, but Demchyshyn said he would ask the major industrial consumers to impose a 'voluntary restriction' in energy consumption.
Ukraine produced more than 60 million tonnes of coal last year, making it self-sufficient in electricity and coal.
Separatist fighting in the Donetsk and Luhansk regions since June has halted production at 66 coal mines, however, leaving Ukrainian power plants without enough raw materials.