Britain is now “directly involved” in the Ukraine war after its Storm Shadow missiles were used to strike targets inside Russia, according to Moscow’s ambassador.

Speaking to Sky News’ Mark Austin, Andrei Kelin also warned the West to carefully consider the lower bar Russia has established for using nuclear weapons.

It comes after Western allies green-lit Ukraine‘s use of long-distance missiles to strike inside Russia this week, following months of requests.

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British Storm Shadow missiles were fired into Russia just days after President Biden authorised the same policy shift.

Russia’s President Putin responded on Thursday by saying Russia had tested a new intermediate-range missile in a strike on the Ukrainian city of Dnipro.

He warned it could also be used against military facilities of countries that allow Kyiv to use their own missiles.

The Russian ambassador told Sky News that Britain allowing Ukraine to use its missiles over the border had dragged the UK into the conflict.

“Absolutely, Britain and UK is now directly involved in this war, because this firing cannot happen without NATO staff, British staff as well,” said Mr Kelin.

He added: “The US administration, support by France and the UK, has made a deliberate decision to make these strikes, which seriously escalates the situation, and it can bring a collision between the nuclear powers.”

Mr Kelin called it “deliberate cheating of us”, claiming he had received multiple assurances the Storm Shadows would only be used inside Ukrainian territory.

Asked what the difference was between Ukraine using British missiles and Russia using Chinese, Iranian and North Korean equipment and manpower – and whether they were also directly involved – Mr Kelin pointed to foreign fighters on the Ukrainian side.

“On that subject, I can say easily that we have plenty of mercenaries from different countries that are fighting right now on the side of Ukraine,” he said.

“We just have seen in the Kursk area of the Polish unit, which has a special uniform worn by Polish soldiers. So what’s the matter?”

In response to Mr Kelin’s comments, a Downing Street spokesperson said the government would not be “deterred or distracted by commentary from Vladimir Putin or the Russian ambassador”.

Until this week, Britain said its tanks, anti-tank missiles and other equipment could be used inside Russia, but had kept restrictions on long-range missiles – echoing America’s policy.

President Putin again raised the spectre of nuclear weapons this week when he approved changes that lower the threshold for such a strike.

Many have dismissed the move as empty sabre rattling, but Russia’s ambassador told Sky News he hoped the change “would be carefully considered by Western experts” as underestimating the risk of escalation is “dangerous”.

Russia ‘uses ballistic missile’

Reports on Thursday suggested Russia may have fired an intercontinental ballistic missile (ICBM) at the Ukrainian city of Dnipro.

President Zelenskyy said the weapon used had the speed and altitude of a ICBM.

He added: “Today, our crazy neighbour has once again shown what he really is and how he despises dignity, freedom, and human life in general. He is so afraid that he is already using new missiles.”

An investigation is under way to confirm the type of missile, Mr Zelenskyy added.

A spokesperson for the British Prime Minister Sir Keir Starmer said reports of the missile’s use were “deeply concerning”.

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However, in his TV address on Thursday evening, President Putin spoke of his forces using a new intermediate-range missile to hit a missile factory in Dnipro.

American officials also said their initial assessment was that the missile was an intermediate-range weapon.

In contrast, an ICBM can travel further – with a ranger greater than 3,500 miles (5,600km) – and is generally used to deliver nuclear warheads.

“We believe that we have the right to use our weapons against military facilities of the countries that allow to use their weapons against our facilities,” Mr Putin said in his TV address.

“And in case of escalation of aggressive actions, we will respond resolutely in a mirror way.”