Russian President Vladimir Putin reviewed exercises conducted by his nuclear-capable forces on Wednesday, as Moscow made unsubstantiated claims to India and China that Ukraine is developing a “dirty bomb.”

The drills are the latest in a series of escalating comments from Moscow and Putin – who were watching the drills from a control room – that Ukraine’s eight-month conflict could turn nuclear.

“A training session involving strategic ground, sea and air defense forces was held under the leadership of … Vladimir Putin, during which practical launches of ballistic and cruise missiles took place,” the Kremlin said in a statement.

Russian state media released footage of a submarine crew preparing to launch a Sineva ballistic missile from the Barents Sea in the Arctic.

The exercises also included the launch of test missiles from the Kamchatka Peninsula in the Russian Far East.

Footage of the drills in state media came after Russia’s Defense Minister Sergei Shoigu pushed for phone calls to his counterparts around the world, claiming Ukraine was developing a “dirty bomb”.

Shoigu, who has been making these claims to his NATO-nation counterparts in recent days, repeated them to his Chinese counterpart Wei Fenghe on Wednesday.

Shoigu also raised the same “concerns” in a phone conversation with India’s Defense Minister Rajnath Singh, Moscow said.

Ukraine has dismissed the allegations as “absurd” and “dangerous,” noting that the claims could mask Russia’s own plans on the battlefield, as well as its Western allies, including Britain, France and the United States.

A dirty bomb is a conventional bomb laced with radioactive, biological, or chemical materials that are dispersed when it explodes.

Kremlin spokesman Dmitry Peskov told reporters earlier Wednesday that Russia had information about the “existing threat” to Ukraine of a “dirty bomb” and that Kyiv was “preparing for such an act of terrorist sabotage.”

He added, “We will continue to vigorously bring our point of view to the global community to encourage them to take active steps to prevent such irresponsible behavior.”

Russia’s nuclear rhetoric began in September when Moscow said it would annex four regions of Ukraine over which its armed forces have partial control. Putin warned Russia not to use nuclear weapons in their defense.

One such region is Kherson in southern Ukraine, near Moscow-annexed Crimea, where Kyiv has been retaking territory since a counter-offensive announced late this summer.

Russian-backed authorities in recent days have urged residents to flee the attack, which they describe as accommodating. They claimed to have turned the city of Kherson into a “fortress” and vowed to defend it at all costs.

A Moscow-based regional official, Vladimir Saldo, said on Wednesday that at least 70,000 people had fled their homes in the last week.

Ukraine’s capture of the Kherson region would give Kyiv back an important gateway to the Sea of ??Azov. It would also cut off Moscow’s land bridge to Russia’s annexed Crimea.

Saldo banned entry to the region’s right bank for seven days “due to the tense situation on the contact line,” according to a statement on his social media on Wednesday.

Russia’s offensive to seize Ukrainian territory sparked a wave of international solidarity with Kyiv, including hundreds of foreigners who volunteered to help repel Russian advances.

Kyiv said on Wednesday Russia had returned the remains of US citizen Joshua Alan Jones, who was killed fighting Moscow forces in August, along with 10 Ukrainian soldiers in a prisoner exchange.