Russian President Vladimir Putin has launched an exercise of the country’s nuclear forces featuring missile launches in a simulation of a retaliatory strike amid soaring tensions with the West over Ukraine.

“Given the growing geopolitical tensions and the emergence of new external threats and risks, it is important to have modern and constantly ready-to-use strategic forces,” Putin said on Tuesday as he announced the exercise.

In televised comments, Minister of Defence Andrei Belousov told Putin that the purpose of the drill was to practise delivering “a massive nuclear strike by strategic offensive forces in response to a nuclear strike by the enemy”.

The exercise involved Russia’s full nuclear “triad” of ground, sea, and air-launched missiles.

A Yars intercontinental ballistic missile was launched from Plesetsk Cosmodrome in northwest Russia to Kamchatka, a peninsula in the Far East. Sineva and Bulava ballistic missiles were fired from submarines, and cruise missiles were launched from strategic bomber planes, the defence ministry said.

The missile exercise took place at a critical moment in the Russia-Ukraine war, after weeks of Russian signals to the West that Moscow would respond if the United States and its allies allowed Kyiv to fire longer-range missiles deep into Russia.

On Monday, NATO said that North Korea had sent troops to western Russia, a claim Moscow has not denied. Last week, Putin stated that Moscow’s implementation of its partnership treaty with Pyongyang is its own business.

The two-and-a-half-year-old war is also entering what Russian officials say is its most dangerous phase as the West considers how to shore up Ukraine while Russian forces advance in the east of the country.

Putin emphasised on Tuesday that Russia’s nuclear arsenal remains a “reliable guarantor of the country’s sovereignty and security”.

“Taking into account growing geopolitical tensions and emerging new threats and risks, it’s important for us to have modern strategic forces that are always ready for combat,” he said, reaffirming that Russia sees nuclear weapons use as “the ultimate, extreme measure of ensuring its security.”

The drill follows an October 18 exercise in the Tver region, northwest of Moscow, involving field movements by a unit equipped with Yars intercontinental ballistic missile capable of striking US cities.

Since the start of the war, Putin has sent a series of pointed signals to the West, shifting Russia’s stance on major nuclear treaties and announcing the deployment of tactical nuclear missiles to neighbouring Belarus.

Ukraine has accused Putin of nuclear blackmail. NATO says it will not be intimidated by Russian threats.

Last month, the Kremlin leader approved changes to the official nuclear doctrine, extending the list of scenarios under which Moscow would consider using such weapons.

Under the changes, Russia would consider any assault on it supported by a nuclear power to be a joint attack – a warning to the United States not to help Ukraine strike deep into Russia with conventional weapons.

Putin has said that Russia does not need to resort to the use of nuclear weapons to achieve victory in Ukraine.

Russia is the world’s largest nuclear power. US officials say they have seen no change to Russia’s nuclear deployment posture during the war. Together, Russia and the US control 88 percent of the world’s nuclear warheads.

In 2022, the United States grew so concerned about Russia’s possible use of tactical nuclear weapons that it warned Putin about the consequences to CIA Director Bill Burns.