Moscow, Russia - Russian President Vladimir Putin lashed out at Washington's support for Kyiv, claiming Ukraine has "de facto" lost its sovereignty and become a tool of the United States, as he renewed unsupported "dirty bomb" claims and oversaw annual nuclear drills.

The US is using Ukraine as a "battering ram" against Russia and other post-Soviet countries, Putin said on Wednesday.

Washington is increasingly arming Ukraine with heavy weapons in its fight against Russian forces, while ignoring the fact that the country is seeking a nuclear bomb, Putin alleged.

"It is also known that there are plans for a provocation to use such a so-called dirty bomb," he said once again, a claim that has been slammed by Kyiv and its allies in the West as "nonsense."

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As its eight-month-old military campaign struggles in Ukraine, the Russian leadership has been saying for days that Kyiv is planning to use a dirty bomb - meaning a conventional explosive device that disperses radioactive material - without providing any evidence.

Washington and European capitals have said it is Moscow that could be planning such an attack on Ukraine.

Russian Defense Minister Sergei Shoigu on Wednesday made phone calls to his counterparts in countries such as China and India to point out such a supposed bomb threat, after holding similar conversations with other capitals earlier in the week.

The Kremlin announced that Moscow was also in talks with the International Atomic Energy Agency (IAEA) on the subject.

Kyiv said it already invited experts from the UN nuclear watchdog to come to Ukraine to see for themselves the baselessness of Russian accusations.

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Putin made his comments during a meeting of representatives from state security bodies of the Commonwealth of Independent States (CIS). The CIS promotes cooperation among former members of the Soviet Union.

Meanwhile, Russia has been testing the operational readiness of its strategic nuclear forces by firing intercontinental ballistic missiles (ICBMs). The maneuver, which lasted several days, had been expected and therefore did not cause concern among Western military officials, despite international tensions over Russia's war in Ukraine.