Russia's defence ministry accused Ukraine on Saturday of planning to attack the Kursk nuclear power plant and blamed such a "provocation" on Moscow.
Interfax news agency cited the ministry as saying.
The ministry said Russia would respond harshly in the event of such an attack, which it said would contaminate a large surrounding area.
Ukraine launched an incursion into Russia's western Kursk region on August 6 and has claimed to have taken control of 82 settlements over an area of 1,150 square kilometres (440 square miles) since then.
The Kursk nuclear power plant, however, remains under Russia's control.
US and Iran signal a peace deal is close
Qatar rejects media report on energy production decisions
Trump says Iran war deal close as Strait of Hormuz tensions linger
Victims' families mark Air India crash anniversary with prayers and tributes
Ebola outbreak spreads to crowded displacement camp in Congo
Fire breaks out at New Zealand's Wellington airport, disrupting flights
Ukraine and Russia trade overnight drone strikes, officials say
UN says Taliban arrest 30 women for violating hijab rules in Afghanistan
