Vladimir Putin today issued a nuclear warning to the West in the event of a "massive" air attack on Russia. This includes the use of cruise missiles which the UK has supplied to Ukraine for Kyiv to target locations deep within Russian territory.

President Putin's remarks came after his urgent meeting with Moscow's top security council to discuss Russia's nuclear deterrence.

Russia's threat comes amid rising concerns in Moscow over Ukraine being allowed by Western powers - especially the UK and US - to use cruise missiles against it.

Last week the UK reportedly cleared the use of its 'Storm Shadow' cruise missile to be used to bomb Russia. UK Prime Minister Keir Starmer even flew to Washington DC to meet US President Joe Biden. The two leaders reportedly discussed Ukraine's use of weapons on Russian soil.

The Russian intelligence had information about such a possibility and had said earlier this month that "It has become necessary for Moscow to revise its nuclear doctrine because of the West's escalation of the war in Ukraine."

Speaking about the reports that the United States and United Kingdom are about to give clearance to Ukraine for Kyiv to launch cruise missiles on Russian soil, President Putin said this month that, "The West would be directly fighting with Russia if it gave such permission to Ukraine (to bomb Russia)" adding that Moscow would be forced to make "appropriate decisions" in such a scenario.

RUSSIA'S NUCLEAR DOCTRINE & TREATY WITH US

Russia is the world's largest nuclear power. Together, Russia and the United States control 88% of the world's nuclear weapons.

Russia's current nuclear doctrine was set in place by Vladimir Putin four years ago, before the war with Ukraine broke out. According to the current doctrine, Russia may use nuclear weapons in the scenario where it comes under a nuclear attack or if a conventional attack threatens the existence of the state.

The United States and Russia have a nuclear treaty called the US-Russia New START Treaty, which entered into force on February 5, 2011.

Under the treaty, the United States and the Russian Federation had seven years to meet the treaty's central limits on strategic offensive arms (by February 5, 2018) and are then obligated to maintain those limits for as long as the treaty remains in force.

According to the US State Department, this treaty enhances US national security by placing verifiable limits on all Russian deployed intercontinental-range nuclear weapons. The United States and the Russian Federation have agreed to extend the treaty through February 4, 2026.

According to a Reuters report, the Kremlin said that any discussions about a replacement to the US-Russia New START Treaty, which expires in 2026, would need to take into account European nuclear potential - shorthand for the arsenals of Britain and France.

"We have not yet received a response from the Americans to this, but of course an agreement is needed and negotiations should begin as soon as possible," Peskov said when asked about a possible replacement for the New START Treaty.

THE STORM SHADOW MISSILE

Ukraine already has the UK-supplied Storm Shadow missile, but uses it only within its territory to combat Russian forces.

So far, there are restriction on Ukraine on the use of advanced western weaponry on targets within the Russian territory, but this is likely to change with clearances reportedly being issued by the UK, with US backing it.

The Storm Shadow is a low-observable, long-range air-launched cruise missile. It is jointly developed by the United Kingdom and France and has a range of around 500 km. It has already been integrated into Ukrainian fighter aircraft, including the Russia-built Su-24 bombers - a legacy of the past, from when Ukraine was part of the erstwhile Soviet Union.

Developed in 1994 and manufactured by Matra and British Aerospace, the Storm Shadow missile is now made by MBDA Systems. 'Storm Shadow' is the weapon's British name, while in France it is called the SCALP-EG.

RUSSIAN NUCLEAR WEAPONS STOCKPILE

Should Ukraine use cruise missiles to attack Russian territory, a Russian response to this could be massive. The international worry is that Moscow may seriously consider the use of nuclear weapons in such a scenario.

According to Center for Arms Control and Non-Proliferation - a nonpartisan non-profit organisation on nuclear weapons disarmament - Russia maintains a stockpile of an estimated 6,372 nuclear warheads - the world's largest.

Of these, 1,572 of which are deployed on strategic land-based ballistic missiles, submarine-launched ballistic missiles, and heavy bombers. Approximately 870 more strategic warheads and 1,870 non-strategic warheads are in reserve with an additional estimated 2,060 warheads awaiting dismantlement.