In recent days, Russian leaders have accused Ukrainian forces of planning to use a weapon no army has ever used. They have floated the idea of a device that would spread radioactive material known as a "dirty bomb." Now, President Vladimir Putin has joined in, creating a pretext for escalating the war.

Putin met with the heads of security services in the former nations of the Soviet Union on Wednesday. He told them Ukrainian authorities plan to provoke his forces by using a "dirty bomb."

Putin said, "The Ukrainian territory has been turned into a testing ground for military biological experiments. And now they are pumping it up with weapons, including heavy ones."

Putin had already warned he is ready to use "all means available." He viewed online an exercise where his forces carried out drills to prepare for a possible enemy attack. They practiced delivering what they called a "massive nuclear strike."

NATO Secretary General Jens Stoltenberg said on Wednesday that Putin's rhetoric is "reckless... and irresponsible."

He added, "Allies reject this blatantly false accusation, and Russia must not use false pretexts to escalate the war further."

Other Western allies have also rejected the Russian claims. The top diplomats from the US, the UK, and France say allegations that the Ukrainians are preparing to use a dirty bomb are "transparently false."