VLADIMIR Putin has ordered up to 50 sleeper agents in Britain to prepare to strike against the UK, it has been claimed.
MI5 believes the Russian leader has instructed the undercover agents to be ready to launch cyber attacks amid soaring tensions with Moscow over the war in Ukraine.
Intelligence chiefs fear that agents will also try to steal military information and target Ukrainian activists and Russian dissidents.
Sources have told the that Russian spies have infiltrated all parts of British society, including top public schools and the civil service.
A senior intelligence insider said: “We have to assume Russia is now active at all levels of British society.
"They scoop up all forms of intelligence and pass it back to the Kremlin through handlers.
READ MORE ON RUSSIA
“This could be anything from what sort of weaponry is being sent to the Ukraine – and how much of it – to the sexual antics of the country’s political and military leaders.”
And former military intelligence officer Lt Col Philip Ingram, told the outlet: “It is impossible to accurately assess how many Russian agents there are in the UK.
“Of course there are different types – declared intelligence officers known as part of Russian diplomatic missions, and those operating under cover trying to recruit agents and then sleeper agents in all aspects of society.
"Given our support for Ukraine, Russian intelligence will be focused heavily on operations inside the UK and could also include recruiting agents inside political establishments, defence and industry”.
Most read in The Sun
The claim comes after The Sun Online revealed that up to four Russian spies are feared to be operating in Westminster.
Former Russian spy Boris Karpichkov, 62, said: "I know of four sleepers of Russian security services.
"There are several Parliament-sponsored organisations operating in Westminster directly linked to Russian security service operations."
Meanwhile, a suspected Russian spook in his 40s was arrested last week, under the Official Secrets Act as he attempted to leave the UK via Gatwick Airport.
He was taken to Hammersmith Police Station accused of spying and sabotage that is "useful to an enemy state".
A source told The Sun: "The suspect is believed to have been in the UK spying on behalf of the Putin regime.
“He was kept under observation and arrested as he arrived at Gatwick to try and fly out of the country.’’
British spy hunters are already on alert for Russian agents seeking to unleash a cyber attack in response to the UK’s support for Ukraine following Russia’s invasion.
Home Secretary Priti Patel previously warned of "cyber attacks aimed at the West" amid Putin's bloody war in Ukraine.
Additionally, Lindy Cameron, head of GCHQ's National Cyber Security Centre (NCSC) warned of a "heightened cyber threat".
Companies and public services were urged to take "pre-emptive measures" to defend themselves against an attack.
A potential cyber-attack by Russia could have devastating consequences and even lead to a war, a Nato official warned.
A cyber attack on the West could trigger Article 5 - its collective defence clause, which was invoked for the first time ever after 9/11.
Nato has made it clear for years that a serious cyberattack could trigger the clause, but such a scenario has so far been hypothetical.
In case of a Russian cyber attack, Nato allies would have to make a "political decision" about whether the strike is large enough to trigger Article 5.
Both Britain and the US have warned Russia could launch cyberattacks on Ukraine - which could impact the rest of the world.
For example, a Russian cyberattack on Ukraine that impacts Poland - a Nato member state - could prompt the deployment of US troops.
On another occasion, last month Russian hackers threatened to shut down ventilators in hospitals across the UK after their comrad was held following a police raid.
The man was arrested under suspicion of assisting Killnet's group high-tech assault on government websites in Romania.
And his alleged comrades warned they would disable NHS ventilators if he is not released.
Cyber crime sources close to the investigation warned last night that the threat was credible.
There are a number of Russian agents previously known to have entered the UK.
Alexander Petrov and Ruslan Boshirov are believed to be behind the Salisbury poisonings of Sergei and Yulia Skripal.
They were caught on CCTV in Salisbury "moments before the attack”.
They were pictured arriving at the local train station, before leaving Britain at Heathrow Airport.
READ MORE SUN STORIES
Read More on The Sun
They stayed in the City Stay Hotel in Bow, East London, during their time in the UK.
Poisoner Dmitry Kovtun was accused of murdering Putin enemy Alexander Litvinenko in London.
We pay for your stories!
Do you have a story for The Sun news desk?
Email us at [email protected] or call 0207 782 4104. You can WhatsApp us on 07423 720 250. We pay for videos too. Click here to upload yours