Russian Foreign Minister Sergei Lavrov supported the statements made by, among others, Defense Minister Sergei Shoigu about the planned Ukrainian production of dirty bombs.
According to Lavrov, the information "has been double-checked".
- We have information that we have checked carefully via the corresponding channels that it is not about unfounded suspicions.
So there are serious reasons to believe that something like that can be planned, he said during a press conference on Monday.
Furthermore, he said he had evidence that work on the bomb was in its final stages.
Dirty bomb
The Russian accusations concern conventional weapons that spread radioactive radiation.
Nonsense replied Kyiv, and in turn was supported by several Western countries: "Our countries made it clear that we all reject Russia's blatantly false accusations that Ukraine is preparing to use a dirty bomb on its own territory", Britain, France and the United States have responded in a joint statement.
Ukraine invites IAEA
US and Russian military chiefs spoke by phone on Monday on the matter, with the US again questioning the Russian data.
The phone call was between Russia's army chief Valery Gerasimov and US military chief General Mark Milley.
According to senior Pentagon officials, there is no indication that Russia is currently considering using nuclear weapons or chemical or biological warfare agents.
Ukrainian Foreign Minister Dmytro Kuleba invited the UN Atomic Energy Agency IAEA to inspect facilities.
Risky excuse
Military observers in the West believe that the Russian moves are attempts to find a pretext for increased military attacks, and NATO Secretary General Jens Stoltenberg shares that view.
"The allies in NATO reject the accusations.
Russia cannot use them as a pretext to escalate.
We continue to stand by Ukraine," he writes on Twitter.