Earlier on Sunday, Sergei Shoigu held phone calls with counterparts from the United States, Britain, France and Turkey alleging that Ukraine was preparing a “provocation” involving a radioactive device.

“If Russia calls and says that Ukraine is allegedly preparing something, it means one thing: Russia has already prepared all this,” Zelensky said in a televised address Sunday evening.

Russia's Defense Ministry said Shoigu voiced concern about “possible Ukrainian provocations involving a ‘dirty bomb,’” a device that uses explosives to scatter radioactive waste.

It doesn’t have the devastating effect of a nuclear explosion, but it could expose broad areas to radioactive contamination.

Russian authorities repeatedly have made allegations that Ukraine could detonate a dirty bomb in a false flag attack and blame it on Moscow.

Ukrainian authorities, in turn, have accused the Kremlin of hatching such a plan.

Zelensky asserted the international community was unlikely to believe Shoigu's claims.

“The very Russian threat of nuclear weapons ... is a reason for both sanctions and for even greater strengthening of support for Ukraine,” he added.

Zelensky also said that power supply had returned to all regions of the country following heavy Russian bombardment on key infrastructure on Saturday.

In its latest war tactic, Russia has intensified strikes on power stations, water supply systems and other key infrastructure in Ukraine.

Zelensky said scheduled power outages were being applied in some regions in order to share power with areas unable to produce sufficient amounts of electricity.