A general view of the Zaporizhzhia NPP power station in Ukraine in this file photo. (Photo/Agencies)

Russian forces seized control of Europe's largest nuclear power plant in southeastern Ukraine on Friday, the Russian Defense Ministry said.

The Zaporizhzhia NPP power station is located on the Dnipro River of Ukraine, and produces a fifth of Ukraine's electricity.

Russian forces took full control of the Zaporizhzhia site after a battle with Ukrainian troops on Friday evening, Russian Defense Ministry spokesman Igor Konashenkov said at a briefing. The fierce fighting set an adjacent training facility of the power station on fire.

The blaze had prompted global concern, with the United States and the United Kingdom calling for an end to fighting in the area.

There was no sign of a radiation leak. Essential equipment at the nuclear power plant was unaffected after the fire, with no change in radiation levels, the International Atomic Energy Agency said.

Of the six reactors at Zaporizhzhia, the State Nuclear Regulatory Inspectorate of Ukraine said one is in operation and producing power, one has been turned off and four are being cooled to prevent overheating.

The regulator did not say, however, what each reactor's status had been before the fire. The Ukrainian nuclear regulator said in a statement that the hours-long fire had been extinguished at 6:20 am local time, and plant staff were continuing to operate the reactor and supply power according to normal safety rules.

The Ukrainian State Emergency Service also said the blaze did not affect "essential" equipment at the plant.

Ukraine's nuclear facilities have been a major point of concern since Russia's "special military operation" last week as the 1986 Chernobyl disaster, also in Ukraine, left hundreds dead and spread radioactive contamination west across Europe.

The fighting between the two countries seemed to be continuing when the second round of talks between Russian and Ukrainian delegations ended on Thursday evening without a cease-fire agreement.

"The second round of negotiations is over. Unfortunately, the results Ukraine needs are not yet achieved," Ukraine's presidential adviser, Mykhailo Podolyak, said on social media following the meeting.

Still, Podolyak said the talks did produce a "solution only for the organization of humanitarian corridors".

Russian Foreign Minister Sergey Lavrov said that Moscow will continue to insist that any peace agreement with Ukraine must include a promise that Ukraine will "demilitarize". Russia has also signaled it wants to discuss Ukraine adopting a "neutral status" and agree to abandon its ambition to join NATO.