Ukraine and several of its allies, including the United States, have rejected a claim from Russia's defense minister, who said that Ukraine was preparing to detonate a "dirty bomb" in its own territory. Russian Defense Minister Sergei Shoigu made the claims in a series of calls with U.S., British, French and Turkish defense officials.
"We reject reports of Minister Shoygu's transparently false allegations that Ukraine is preparing to use a dirty bomb on its own territory. The world would see through any attempt to use this allegation as a pretext for escalation." said U.S. National Security Coucil spokesperson Adrienne Watson.
A "dirty bomb" uses conventional explosives to spew radiological materials into the air and contaminate the surrounding area. The size of the area contaminated would depend on the size of the explosion.
Russian authorities repeatedly have made allegations that Ukraine could detonate a dirty bomb in a false flag attack and blame it on Moscow. Ukrainian authorities, in turn, have accused the Kremlin of hatching such a plan.
British Defense Secretary Ben Wallace strongly rejected Shoigu's claim and warned Moscow against using it as a pretext for escalation.
The British Ministry of Defense noted that Shoigu, in a call with Wallace, "alleged that Ukraine was planning actions facilitated by Western countries, including the UK, to escalate the conflict in Ukraine."
"The Defense Secretary refuted these claims and cautioned that such allegations should not be used as a pretext for greater escalation," the ministry said.
In a televised address Sunday evening, Ukrainian President Volodymyr Zelenskyy suggested that Moscow itself was setting the stage for deploying a radioactive device on Ukrainian soil.
"If Russia calls and says that Ukraine is allegedly preparing something, it means only one thing: that Russia has already prepared all of it," Zelenskyy said.
The mention of the dirty bomb threat in Shoigu's calls seemed to indicate the threat of such an attack has risen to an unprecedented level.
The French Ministry of the Armed Forces said Shoigu told his counterpart, Sebastien Lecornu, that the situation in Ukraine was rapidly worsening and "trending towards uncontrollable escalation."
"It appears that there is a shared feeling that the tensions have approached the level that could raise the real threat for all," said Fyodor Lukyanov, the Kremlin-connected head of the Council for Foreign and Defense policies, a Moscow-based group of top foreign affairs experts.
The rising tensions come as Russian authorities reported building defensive positions in occupied areas of Ukraine and border regions of Russia, reflecting fears that Ukrainian forces may attack along new sections of the 1,000-kilometer (620-mile) front line of the war, which enters its ninth month on Monday.