KYIV, Ukraine - NATO and Russia’s military alike staged planned annual nuclear exercises Wednesday as the Russian president repeated the unfounded claim that Ukraine plans to set off a radioactive “dirty bomb.” On the battlefront, Russian forces pounded more than 40 Ukrainian villages over the past day.

Russian President Vladimir Putin remotely monitored the drills of his strategic nuclear forces, which involved multiple practice launches of ballistic and cruise missiles in a show of force. Russian Defense Minister Sergei Shoigu reported to Putin that the exercise simulated a “massive nuclear strike” retaliating for a nuclear attack on Russia.

The Biden administration said Russia provided advance notice of the annual drills. NATO is carrying out its own long-planned annual nuclear exercises in northwestern Europe.

Without providing any evidence, in remarks carried by Russian TV, Putin said Ukraine plans to “use a so-called ‘dirty bomb’ as a provocation” and contended the United States was using Ukraine as a “battering ram” against Russia and its regional allies, turning the country into a “testing ground for military-biological experiments.” It was the first time Putin himself made the unsubstantiated dirty bomb allegation, which his officials have been repeating since last week.

Ukraine and its Western allies have denied the claims and contend that Russia, facing setbacks on the battlefield, might itself try to detonate a “dirty bomb” - which uses explosives to scatter radioactive waste to sow terror - or go further and tap its vast nuclear weapon arsenal.

Shoigu on Wednesday called his counterparts from India and China to share Moscow’s concern about “possible Ukrainian provocations involving a ‘dirty bomb,’” according to the Russian Defense Ministry.

NATO Secretary-General Jens Stoltenberg called Russia’s unsubstantiated statements “absurd.”

“Allies reject this blatantly false accusation, and Russia must not use false pretexts to escalate the war further,” Stoltenberg told reporters at NATO headquarters in Brussels on Wednesday.

He underlined that the 30-nation military organization “will not be intimidated or deterred from supporting Ukraine’s right to self-defense for as long as it takes.”

Despite the Western dismissals, Kremlin spokesman Dmitry Peskov insisted that Moscow had information about “an ongoing preparation in Ukraine for such a terror attack.”

Slovenia’s government said Russia has been engaging in a disinformation campaign about the “dirty bombs,” using a 2010 photo from the European Union country’s Agency for Radioactive Waste titled “Ukraine’s capacities to create the dirty bomb.” The photo shows bags containing smoke detectors bearing inscriptions in Slovenian reading “radioaktivno,” or radioactive. The Slovenian government says the detectors contain a radioactive source but it isn’t one of those listed below the photo in the Russian Foreign Ministry release. Slovenia’s government said on Twitter that its radioactive waste is stored safely and is not used for dirty bombs.

While continuing to issue unsubstantiated claims that Ukraine is planning provocations, Putin also is still sending signals that he’s open to negotiations with Kyiv. The latest message came via Umaro Mokhtar Sissoco Embalo, President of Guinea Bissau, who visited Kyiv to meet with President Volodymr Zelenskyy.

“I was in Russia with President Putin, who asked me to forward you what we spoke about, something he thinks would be very important. He wishes and thinks that a direct dialogue should happen between your two countries,” the Guinea Bissau leader said.

Zelenskyy responded that a prerequisite for talks would be Russia’s recognition of Ukraine’s territory, borders and sovereignty.

On the battlefront, Ukrainian officials said fighting in more than 40 villages killed at least two civilians and sustained the terror that forces people into air raid shelters each night.

Russian forces launched five rockets, 30 air strikes and more than 100 multiple-launch rocket system attacks on Ukrainian targets, the Ukrainian armed forces general staff said.