Russia's defense minister has alleged that Ukraine may use a so-called dirty bomb -- a claim that Kyiv dismissed as "lies."

Russia's defense ministry announced that Sergei Shoigu had a series of telephone talks with his counterparts of the US and some other NATO member nations on Sunday.

Without providing evidence, Shoigu told the defense chiefs of France, Turkey and Britain that Russia is concerned Ukraine could use a dirty bomb, or conventional explosive that scatters radioactive material.

Ukrainian President Volodymyr Zelenskyy denounced the allegation.

Zelenskyy said in a video message on Sunday that everyone understands "who is the source of everything dirty that can be imagined in this war."

He said, "It was Russia who blackmailed with the radiation disaster" at the Zaporizhzhia nuclear power plant.

Monday marks eight months since Russia began its invasion of Ukraine. Ukrainian forces have been advancing in the eastern and southern regions since September, aiming to retake more territory from Russia.

They are stepping up counteroffensives in the southern region of Kherson, which was unilaterally annexed by Moscow.