Earlier, Theresa May announced a package of anti-Russian measures, including the expulsion of Russian diplomats from the country and the suspension of bilateral contacts between London and Moscow after former Russian intelligence officer Sergei Skripal and his daughter were found unconscious in a shopping center in Salisbury.
"Since the UK side was given a week, most of them will leave at the end of this week," the source said.
On Saturday, the Russian Foreign Ministry summoned UK Ambassador Laurie Bristow and announced that 23 UK diplomats would be expelled from Russia, while the operation of the British Council would be ceased in the country. The move came as a response to the expulsion of 23 Russian diplomats from the United Kingdom over allegations that Russia was behind the poisoning of former Russian spy Sergei Skripal with A234 chemical agent.
Skripal and his daughter Yulia were found unconscious earlier this month at a shopping center in Salisbury. Both of them stay in critical condition and are being treated for exposure to a chemical.
Previously, Russian ex-intelligence agent Skripal had been accused of espionage on behalf of the UK. He fled the country and was later granted asylum in the United Kingdom after a US-Russia spy exchange.