The U.N. nuclear watchdog said Thursday it found no signs of undeclared nuclear activity at three sites in Ukraine it inspected at Kyiv’s request in response to Russian accusations that Ukraine was working on a “dirty bomb.” At the same time, the Minister of Foreign Affairs of Ukraine, Dmytro Kuleba, reacts sharply to the Kremlin, saying that Russia has “confirmed its status as the biggest liar in the world” by accusing Ukraine of a “dirty bomb”.

“Our technical and scientific assessment of the results we obtained did not show any signs of undeclared nuclear activity and materials at these three sites,” the International Atomic Energy Agency said, adding that environmental samples taken would be analyzed, Reuters reported.

Last week, Vladimir Putin said that Russia “knows that a ‘dirty bomb’ incident is being prepared” and that Russia knows “where in the world it is being prepared”.

Concerns about the escalation of the conflict have increased in recent days after repeated “warnings” from Moscow that Ukraine was preparing to detonate a “dirty bomb” on its own territory to blame Russia. Kyiv strongly denies these accusations.

Kyiv says that Russia has “confirmed its status as the biggest liar in the world”

Minister of Foreign Affairs of Ukraine Dmytro Kuleba sharply reacted to the results of the nuclear inspection on Twitter, noting that Russia “confirmed its status as the biggest liar in the world.”

“The IAEA inspected three Ukrainian facilities that were at the center of Russian disinformation and found no evidence of ‘dirty bombs.’ I thank Rafael Mariano Grossi for the excellent and prompt cooperation of the IAEA, which helped counter Russian disinformation. Russia has confirmed its status as the biggest liar in the world.”

A White House adviser said on Wednesday that in recent months the United States has been “increasingly concerned” about a potential nuclear attack by Russia in the context of the war in Ukraine.

The Russian military leadership is discussing when and how Moscow will use tactical nuclear weapons

Russian military leaders have recently engaged in a debate, not including Vladimir Putin, about when and how Moscow might use tactical nuclear weapons in Ukraine.

Information about these discussions was shared in the US administration in mid-October.

CIA Director William J. Burns, however, said that Putin’s “potential desperation” to achieve victory in Ukraine and failures in the war could compel Russia to use such weapons of mass destruction.