VLADIMIR Putin has reportedly ordered an international manhunt for a Russian 'mole' who helped MI5 identify the Novichok assassins.

Kremlin intelligence chiefs were blindsided by Britain identifying Alexander Petrov and Ruslan Boshirov as GRU officers last month - and believe a traitor was responsible for their unmasking.

A spy source told The Daily Mirror: "Clearly our intelligence agencies have very solid intelligence on these two and it may never publicly be known what it is.

“But Putin has been given a very clear message behind the Prime Minister’s identifying of this pair as GRU - and that is that Britain is also on the offensive and can penetrate his intelligence community.

“They will want desperately to find out how MI5 has been able to assure the Prime Minister these men are GRU with absolute confidence after painstaking intelligence gathering.

“Whatever the information is that they have - it was enough for her confidently to warn that the British government will dismantle their operation.”

Moscow spymasters have reportedly ordered a massive security review - and are examining staff logs to see if any employees have behaved "unusually" in recent weeks.

It comes after the pair claimed they were just tourists visiting Stonehenge and Salisbury in an bizarre interview with the state-run TV station RT on September 13.

Ex-KGB spy Sergei and his daughter Yulia, 33, were exposed to the deadly nerve agent in Salisbury on Sunday, March 4, 2018.

They were found slumped on a bench in a "catatonic state" and spent weeks critically ill in hospital before being discharged.

The suspected assassins said: "Our friends had been telling us for some time we should visit this extraordinary town."

Claiming to be interested in the history of the local area, the pair praised Salisbury Cathedral for its "123-metre spire and its clock, one of the first ever created in the world that's still working".

Despite being filmed "moments before" the botched hit before leaving the country hours later in a flight out of Heathrow, the brazen Russians claimed they spent "no more than an hour" in Salisbury.