Russia says it used a military exercise to simulate "delivering a massive nuclear strike” in response to an enemy attack.
The annual exercise on Wednesday used test launches to put Moscow's nuclear forces through their paces in a show of force designed to deter and intimidate foes.
It involved nuclear submarines, strategic bombers and ballistic missiles at a time when tensions are high over a "dirty bomb" allegation the Kremlin has made against Ukraine which Western leaders fear Moscow plans to manipulate to escalate the Ukraine crisis.
Putin later told a meeting of intelligence officials from ex-Soviet countries that the potential for conflict in the world remained high.
"There are new risks and challenges for our collective security," he said.
Providing an update on the drills on Russia television, defence minister Sergei Shoigu told Putin – who observed the exercises remotely – that forces were preparing in the event it was necessary to deliver "a massive nuclear strike by strategic offensive forces in response to an enemy nuclear strike".
Chief of staff Valery Gerasimov added that the exercise involved Yars intercontinental ballistic missiles, submarines and Tupolev strategic bomber planes.
Watch: Putin oversees practice drill of 'huge nuclear strike'
A Kremlin statement said: "The tasks envisaged during the training of the strategic deterrence forces were completed in full, all missiles reached their targets.”
Russia has been accused of stoking misinformation by claiming Ukraine – backed by the West – is planning to detonate a "dirty bomb" to escalate the crisis.
It is feared Russia could use this to launch its own escalation.
On Sunday, Shoigu told Western defence ministers – without providing any evidence – that Moscow believed Ukraine was preparing to detonate a device using conventional explosives packed with radioactive material to spread contamination over a wide area.
After weeks of rising international tension following threats by Putin to defend Russia's "territorial integrity" with nuclear weapons, this was the first concrete statement from Moscow indicating a change in its forces' state of preparedness.
Ukrainian president Volodymyr Zelenskyy responded by accusing Russia of planning such an attack itself to blame on Ukraine.
The US, UK and France also released a joint statement rejecting "Russia's transparently false allegations that Ukraine is preparing to use a dirty bomb on its own territory".
Nato secretary general Jens Stoltenberg also said the organisation "rejected this allegation. Russia must not use it as a pretext for escalation."
At the weekend, Shoigu spoke with US defence secretary Lloyd Austin for the second time in three days as well as UK defence secretary Ben Wallace.
Wallace vehemently rejected Russian claims that Western powers are colluding with Ukraine around a “dirty bomb”.
The head of the British armed forces Admiral Sir Tony Radakin also used a call with his Russian counterpart General Valery Gerasimov to restate Britain's support for Ukraine.
An MoD spokesman said that both military leaders had agreed the importance of maintaining open channels of communication between the UK and Russia to manage the risk of miscalculation and to "facilitate de-escalation".
Meanwhile, in a phone call on Tuesday, US president Joe Biden and new British prime minister Rishi Sunak reaffirmed their two countries' "special relationship" and agreed on the importance of supporting Ukraine, the White House said in a statement.