UN nuclear inspectors found no indication of "undeclared nuclear activities" at three sites in Ukraine, during visits requested by Kyiv to address Russia's "dirty bomb" accusations, the International Atomic Energy Agency said on Thursday.
"Our technical and scientific evaluation of the results we have so far did not show any sign of undeclared nuclear activities and materials at these three locations," said Rafael Grossi, head of the IAEA.
"We will report on the results of the environmental sampling as soon as possible."
Mr Grossi was referring to samples collected by IAEA inspectors.
The inspections at the Institute for Nuclear Research in Kyiv, the Eastern Mining and Processing Plant in Zhovti Vody and the Production Association Pivdennyi Machine-Building Plant in Dnipro followed a written request from Ukraine.
"Over the past few days, the inspectors were able to carry out all activities that the IAEA had planned to conduct and were given unfettered access to the locations," the UN agency said.
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The UN atomic agency's conclusion is "obvious" given "irrefutable evidence" of the absence of any dirty bomb, Ukrainian President Volodymyr Zelenskyy said on Thursday.
"The conclusion of the IAEA today is quite obvious," Mr Zelenskyy said.
"We have given them full freedom of action at the relevant facilities, and we have clear and irrefutable evidence that no one in Ukraine has created or is creating any 'dirty bombs'."
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On Monday the UN nuclear watchdog said its inspectors had begun verification activities at two locations in Ukraine.
A request to visit a third site in Ukraine was later made by Kyiv after Russia made accusations about activities there too, an IAEA spokesman told AFP.
The Kremlin accused Ukraine of preparing to use dirty bombs against Russian troops, while Kyiv suspects Moscow might use a dirty bomb in a "false flag" attack, possibly to justify use of conventional nuclear weapons as ground troops experience setbacks.
A dirty bomb is a conventional bomb laced with radioactive, biological or chemical materials that are spread in an explosion.
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Russian President Vladimir Putin had previously called for the IAEA to inspect Ukraine's nuclear sites "as fast as possible".
After the IAEA's announcement, UK Foreign Secretary James Cleverly said Russia had a history of making false claims to provide cover for its own actions.
But Mr Cleverly said the world could see through this attempt to use false allegations as a pretext for escalation.