IAEA visited sites at Ukraine’s request, following dirty-bomb allegations by Russia 

BERLIN—The United Nations atomic agency said this week’s inspections in Ukraine found no evidence of activities or nuclear material that hadn’t been declared by Kyiv, rebuffing Russian allegations that the country was working on a dirty bomb.

The agency’s Thursday statement, which came after it sent inspectors to three sites in Ukraine at Kyiv’s request, is the latest pushback against Russian allegations against Ukraine and its Western allies. On Wednesday, the U.N. Security Council defeated a Russian resolution alleging there were biological weapons in 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 International Atomic Energy Agency said in a statement. “Based on the evaluation of the results available to date and the information provided by Ukraine, the agency did not find any indications of undeclared nuclear activities and materials at the locations.”

Last month, Russian Defense Minister Sergei Shoigu made a rare round of telephone calls with his U.S., French, U.K. and Turkish counterparts, claiming that the war in Ukraine was moving toward a more dangerous phase and that Kyiv might soon deploy a dirty bomb.

Mr. Shiogu’s claims were echoed by a Russian letter circulated at the U.N. Security Council, which alleged Ukraine would use a dirty bomb in Ukraine as a pretext for claiming that Russia had launched a tactical nuclear weapon against the country and sparking a Western response.

Western officials swiftly dismissed the Russian claim as false, and Washington warned that Russia could be signaling that it is preparing to use such weapons itself in a false-flag operation.

Nuclear experts also dismissed the Russian claim, noting that it would be impossible to pass a dirty bomb attack off as a nuclear weapon, because of the differences that can be swiftly detected during the explosion and the aftermath of the use of each type of weapon. No dirty bomb has ever been successfully deployed.