“We recommend that Russian citizens refrain from visiting mass public events and crowded places in British metropolises unless this is dictated by extreme personal or official necessity,” she said.
The embassy said the British secret services had advised further terror attacks “are inevitable”, and the advice not to travel to the UK would remain until “the situation is stabilised by the state authorities”, and the threat level lowered.
Russians already in Britain were urged to follow official announcements on new threats, follow media advice, avoid crowds and be “very careful” using public transport.
An anonymous diplomat added: "The British government has raised the level of terror threat to 'critical'....the fifth level of a 5 level scale.
"It supposes that, as the secret services say, terror attacks are 'inevitable in the coming future'.
The diplomat warned that the centres of major cities were vulnerable to attacks.
"Within the last three months the terrorist activity is only growing in the country," said the diplomat.
"We do not exclude that this is due to the growing influence of Islamic radicalism in the national communities who live in
"Having called army to patrol the infrastructure is a sign of a very serious situation.
"Because the next act of terror is 'inevitable in the coming future', we do not have any other choice but to recommend Russians to refrain from visiting the UK until the situation is fully under control and the level of threat is officially decreased, unless such trips are extremely important due to business or personal reasons".
Russians in Britain were asked to "understand" that the authorities might carry out tougher checks.
"Be particularly concerned about the safety of your children," Russians were told.
Abedi may have been given a crucial component for his device at a German airport en route to his terror mission, it has been revealed.
Security officials are checking CCTV for possible contact between the 22-year-old and terror suspects in Dusseldorf.
Immediately after the attack police began a desperate race to find the bomb gang behind the Manchester Arena massacre on Monday night.
A total of ten people have now been arrested over the devastating attack, with two released without charge and eight still in custody.