Yakovenko told the Rossiya-24 TV channel that the embassy was receiving "negative letters" vowing "to take reprisals against diplomats."
"There are quite a lot of mentally unbalanced people and people with a criminal past. You can expect anything from them. I have to say that we are cooperating closely with the UK authorities on this matter," he stated.
The ambassador's comment refers to the UK decision to expel 23 Russian diplomats, with London blaming Moscow for the March 4 alleged poisoning of a former Russian intelligence officer Sergei Skripal. Skripal and his daughter Yulia were found slumped unconscious on a bench in Salisbury after being exposed to what British experts have identified as a Russia-made nerve agent.
READ MORE: 'Novichok' Formula Was Published in a Book - Ex French Intelligence Officer
Russian officials have denied all accusations. Moscow has expressed readiness to collaborate on the investigation into this case and requested access to the samples of the nerve agent, however, London has denied this request.
WATCH: CCTV Footage of Skripal Right Before He Was Found Poisoned
