A fleet of unidentified drones flew over three airbases in the UK, including one due to store nuclear warheads.

It is not clear whether the unmanned drones over RAF Lakenheath and RAF Mildenhall, in Suffolk, and RAF Feltwell, in Norfolk, were operated by a hostile actor.

But the sightings between November 20 and 22 came at a tense moment for the British and US militaries based there.

Russian President Vladimir Putin this week threatened to launch strikes on military targets here after Ukraine fired British and American long-range missiles into Russian territory for the first time.

Putin has also lowered the bar for using nuclear weapons, tweaking the country’s official nuclear doctrine so they can be used in response to conventional strikes supported by nuclear powers.

RAF Lakenheath has previously been identified as a possible prime target should Russia ever launch a direct missile attack on the UK.

This is because plans are in motion to house US nuclear warheads – more powerful than the Hiroshima bomb – there for the first time in 15 years.

As home to the US Air Force’s 48th Fighter Wing – with its F-15 and F35A fighter jets – the base would also play a crucial role in any US or NATO military operations in Europe.

There have been unconfirmed reports of F-15E Strike Eagles setting off to chase the drones, as reported by defence news site The War Zone.

But the US Air Force refused to comment on whether any defence mechanisms were used. It did say it retains ‘the right to protect’ installation.

A spokesperson said: ‘We can confirm that small unmanned aerial systems (UASs) were spotted in the vicinity of and over RAF Lakenheath, RAF Mildenhall, and RAF Feltwell between Nov 20 and 22.

‘The number of UASs fluctuated and they ranged in size/configuration.

‘The UASs were actively monitored and installation leaders determined that none of the incursions impacted base residents or critical infrastructure.

‘To protect operational security, we do not discuss our specific force protection measures but retain the right to protect the installation.

‘We continue to monitor our airspace and are working with host-nation authorities and mission partners to ensure the safety of base personnel, facilities and assets.’

Drones were also spotted over a US Army base in New Jersey this week, which is being investigated by the FBI.

Plans to store nuclear warheads at RAF Lakenheath were revealed in documents from the US Department of Defence’s procurement database earlier this year.

At the time, Hans Kristensen, from the Federation of American Scientists, warned it could make the base more of a target in a conflict with Russia.

He said: ‘There is no doubt that if you have nuclear weapons on a base, that base is more likely to be targeted in a nuclear conflict with Russia.

‘There is no doubt that once you have nuclear weapons in, it is a different ball game.

‘If I am a Russian military planner, I am already going to hit it. If you watch Russian television, they talk about the UK a lot; they talk about nuking the UK a lot.’

Fears of a nuclear confrontation are growing as Russia ramps up rhetoric and military power over its war in Ukraine.

Thousands of North Korean troops have amassed on the border with Ukraine.

It marks a change in North Korea’s role in the conflict after supplying millions of missiles and munitions to Russia in the last two years.

This has prompted the UK and US to change conditions attached to their supply of missiles to Ukraine.

Previously they had banned the country from using their weapons to strike within Russia, despite Russia routinely launching missile strikes on Ukraine from within Russian territory.

Now the UK and US have allowed Ukraine to strike military and defence industry targets within Russia itself, drawing the ire of Vladimir Putin.

In response, Russia fired an experimental hypersonic medium or intermediate range ballistic missile, called Oreshnik, at a rocket factory in the Ukrainian city of Dnipro.

Initial fears that this was a nuclear-capable intercontinental ballistic missile – which would have been the first such use in war – were later dismissed.

That night, in his daily video address, Ukrainian President Volodymyr Zelenskyy said: ‘Today, our crazy neighbour has once again shown what he really is and how he despises dignity, freedom, and human life in general. And how afraid he is.

‘He is so afraid that he is already using new missiles. And he is looking around the world for weapons. Sometimes in Iran, sometimes in North Korea.’

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