Russia conducted its first major nuclear drills since the start of its war on Ukraine and President Vladimir Putin made unfounded claims that Kyiv was seeking to develop a “dirty bomb”, as Moscow continued to ramp up the rhetoric over possible nuclear use in the conflict.

The Russian armed forces on Wednesday practised what defence minister Sergei Shoigu called a “mass nuclear strike with strategic attack forces in response to a nuclear attack by our adversary”, as Putin monitored events via videoconference from the Kremlin.

Addressing security chiefs from a group of ex-Soviet countries after the exercises, Putin said “geopolitical confrontation has sharply increased” and accused the US of using Ukraine as a “battering ram” against Russia.

He repeated claims, without providing evidence, that the US had made Ukraine a “test site for military biological experiments”, complaining that the west was “pumping it up with weapons” and ignoring “provocations” using a dirty bomb, a conventional explosive carrying radioactive material.

Kyiv has vehemently denied the claims and said the Kremlin’s aim was that the spectre of nuclear war would pressure Ukraine’s western backers to accept a peace deal on Russia’s terms.

Ukraine’s defence minister Oleksiy Reznikov said he was “absolutely sure” that Putin’s nuclear rhetoric was part of the “blackmailing of our western partners”, meant to discourage them from providing further weaponry to Kyiv.

Russia’s “Grom” drills tested the three parts of Russia’s nuclear capabilities: the RS-24 Yars intercontinental ballistic missile, the missile-carrying K-114 Tula submarine, and two Tu-95 long-range strategic nuclear bombers.

The drills are taking place alongside Nato’s annual nuclear forces exercise, which the alliance has said is designed to ensure that the western nuclear deterrents are “safe, secure and effective”.

Nato’s “Steadfast Noon” drills, which test airborne nuclear forces but no live-fire elements, began this month and will run until October 30 in Belgium, the UK and over the North Sea.

“Nato will not be intimidated or deterred from supporting Ukraine’s right to self-defence,” Nato secretary-general Jens Stoltenberg said on Wednesday, a day after rejecting suggestions that the two nuclear drills running concurrently could further heighten already fraught tensions over the war.

“It would have sent an absolutely wrong signal if then suddenly we cancelled that exercise. We’ve also been transparent about the fact we’re conducting these exercises, and it was planned long before the Russian invasion of Ukraine,” Stoltenberg said a day earlier.

Brigadier General Patrick Ryder, the Pentagon press secretary, said Russia had notified the US about the drills. “This is a routine annual exercise by Russia,” he said, adding that “in this regard, Russia is complying with its arms control obligations, and its transparency commitments to make those notifications”.

The Russian exercises come amid heightened nuclear rhetoric that western countries fear is an ominous attempt by the Kremlin to fabricate a pretext to escalate Putin’s faltering eight-month invasion of Ukraine.

Ukraine’s counteroffensive continues to inflict humiliating setbacks on Russia’s military, pushing Putin to dial up the rhetoric around the use of nuclear weapons.

Russia held the previous exercise in February just days before Putin launched his invasion of Ukraine and warned the west of “consequences you have never encountered in your history” if it tried to stop him.

Last month, he said Russia would use “all the means at our disposal” to defend itself after annexing four regions of Ukraine and warned that the US created “a precedent” when it dropped nuclear bombs on two Japanese cities at the end of the second world war.

Since then, Ukraine has continued to claw back territory Putin has only just claimed as part of Russia and closed in on Kherson, the only regional capital Moscow has captured throughout the war.

The Grom drills followed calls by Shoigu to his counterparts in China and India, where he repeated the dirty bomb claims. These calls followed similar warnings he made over the weekend to the defence ministers of the US, UK and France — Nato’s three nuclear powers — as well as Turkey, which does not have nuclear weapons but has sought to carve out a role as a mediator in the war.

Ukraine believes Putin has not abandoned his goal to essentially destroy the country in its current form and that he was not prepared to negotiate with Kyiv in good faith.

Russia has left swaths of Ukraine without power after stepping up air strikes on the country’s critical infrastructure facilities such as power plants.

Kyiv had pleaded for help to combat Russia’s onslaught from cruise missiles, air strikes and Iran-made drones. Ukraine is set to receive its first batch of Nasams air defence systems from the US, the most sophisticated air defence system provided to Ukraine so far, according to manufacturer Raytheon.