"According to the information we have, two organisations in Ukraine have specific instructions to create a so-called 'dirty bomb'. This work is in its final stage," Lieutenant General Igor Kirillov said in a statement on Monday.

He said Kyiv was planning to accuse Russia of "using weapons of mass destruction in Ukraine and thus launch a powerful anti-Russian campaign in the world".

The weapon would be composed of radioactive elements "creating radioactive contamination over large areas, and potentially also leading to radiation diseases" after detonation.

Ukraine's foreign minister Dmytro Kuleba said UN nuclear agency (IAEA) chief Rafael Grossi accepted his request to "urgently send experts to peaceful facilities in Ukraine which Russia deceitfully claims to be developing a dirty bomb."

The United Kingdom, the United States and France issued a joint statement dismissing the claim earlier on Monday.

"Our countries made clear that we all reject Russia's transparently false allegations that Ukraine is preparing to use a dirty bomb on its own territory," according to the statement.

Russian Foreign Minister Sergei Lavrov said the reaction from the West was "in line with their reckless support for their protege (Ukraine President Volodymyr) Zelensky, their indulgence for his Russophobic actions and destruction of civilian population," during a press conference Monday.

Zelensky on Sunday refuted the accusation and called for a harsh answer from the West.

"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 video address on social media.