The International Atomic Energy Agency (IAEA) announced on Monday evening that it had begun its inspections in Ukraine, requested by this country after Russian President Vladimir Putin accused it of erasing evidence of the preparation of a "bomb dirty".

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IAEA inspectors have "begun -- and will soon complete -- verifying the activities of two sites in Ukraine," the Vienna-based UN agency said in a statement.

IAEA Director General Rafael Grossi said he would release "his first conclusions on the verification activities of the two sites" later this week, according to the statement.

The inspections follow a written request from the Ukrainian government to send IAEA teams on site.

Russia has accused Ukraine of preparing to use dirty bombs against its troops, but kyiv suspects Russia of wanting to use a dirty bomb itself and trying to blame it, perhaps to justify the use of conventional nuclear weapons by Moscow, whose troops are losing ground in eastern and southern Ukraine.

The agency said last week that it inspected "one of the two sites a month ago and no undeclared nuclear activity or material was found there."

A dirty bomb is a conventional bomb surrounded by radioactive, biological or chemical materials that are released during the explosion.

On Thursday, Russian President Vladimir Putin asked the IAEA to inspect Ukrainian nuclear sites "as soon as possible".