Russia sent a letter on its claims about Kyiv to the United Nations late on Monday, and diplomats said Moscow planned to raise the issue with the Security Council at a closed meeting the following day.
“We will regard the use of the dirty bomb by the Kyiv regime as an act of nuclear terrorism,” Russia’s U.N. Ambassador Vassily Nebenzia wrote U.N. Secretary-General Antonio Guterres and the Security Council in the letter, seen by Reuters.
With Ukrainian forces advancing into Russian-occupied Kherson province, top Russian officials had phoned their Western counterparts on Sunday and Monday to air their suspicions.
The foreign ministers of France, Britain and the United States rejected Moscow’s allegations as “transparently false” and reiterated their support for Ukraine.
“The world would see through any attempt to use this allegation as a pretext for escalation,” they said in a joint statement.
Later, the United States issued a warning to Moscow.
“We’ve been very clear with the Russians … about the severe consequences that would result from nuclear use,” State Department spokesman Ned Price said. “There would be consequences for Russia whether it uses a dirty bomb or a nuclear bomb.”
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Russia’s defense ministry said the aim of a “dirty bomb” attack by Ukraine would be to blame Russia for the resulting radioactive contamination. The ministry has begun preparing for such a scenario, it said, readying forces and resources “to perform tasks in conditions of radioactive contamination.”
The U.N. nuclear watchdog said on Monday it was preparing to send inspectors in the coming days to two Ukrainian sites at Kyiv’s request, in an apparent reaction to the Russian “dirty bomb” claims. It said both sites were already subject to its inspections and one was inspected a month ago.
Russia’s state news agency RIA had earlier identified what it said were the two sites involved in the operation — the Eastern Mineral Enrichment Plant in central Dnipropetrovsk region and the Institute for Nuclear Research in Kyiv. The IAEA statement did not name the facilities it would inspect.
U.S. officials said there was no indication Moscow had made the decision to use a dirty bomb or any nuclear weapon.
“We continue to see nothing in the way of preparations by the Russian side for the use of nuclear weapons,” White House national security spokesman John Kirby told reporters.
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Ukrainian President Volodymyr Zelenskiy said the Russian accusation was a sign Moscow was planning such an attack itself and would blame Ukraine.
“If Russia calls and says that Ukraine is allegedly preparing something, it means one thing: Russia has already prepared all this,” Zelenskiy said in an overnight address.
Ukrainian foreign minister Dmytro Kuleba said late Monday he had a detailed discussion with U.S. Secretary of State Antony Blinken on “ways to end Russia’s nuclear blackmail.”
Russia has ordered civilians to evacuate territory it controls on the western bank of the Dnipro River, where Ukrainian forces have been advancing this month shortly after Moscow claimed to have annexed the area.
A Russian defeat there would be one of Moscow’s biggest setbacks yet since its invasion eight months ago.
Kherson’s regional capital is the only big city Russia has captured intact since its Feb. 24 invasion, and its only foothold on the west bank of the Dnipro, which bisects Ukraine. The province controls the gateway to Crimea, the peninsula Russia seized and claimed to annex in 2014.
The Russian-installed authorities in Kherson announced on Monday that men who stay behind would have the option of joining a military self-defense unit. Kyiv accuses Russia of press-ganging men in occupied areas into military formations, a war crime under the Geneva Conventions.
Kyrylo Budanov, Ukraine’s military spy chief, said Russian forces were preparing to defend Kherson city, not retreat.
“They are creating the illusion that all is lost. Yet at the same time they are moving new military units in and preparing to defend the streets of Kherson,” he told the Ukrainska Pravda online media outlet.
Since Russia’s forces suffered major battlefield defeats in September, President Vladimir Putin has escalated the war, calling up hundreds of thousands of reservists, announcing the annexation of occupied territory and repeatedly threatening to use nuclear weapons to defend Russian land.
This month, Russia started a new campaign using long-range cruise missiles and Iranian-made drones to attack Ukraine’s energy infrastructure before winter sets in.
(Reporting by Reuters bureaux; Writing by Doina Chiacu, Editing by Cynthia Osterman)