The man is believed to have traveled to Ukraine on multiple occasions, including during the Maidan events in December 2013, also under the alias of Alexander Petrov, used during his Salisbury mission.
Bellingcat also said it had obtained a copy of Mishkin's passport and that a facial recognition analysis of the passport photograph showed it matched a photo of 'Petrov.' Russian officials have dismissed Bellingcat's previous reports, but have refused to engage with their substance.
One of the two suspects in the poisoning of an ex-spy in England is a doctor who works for Russian military intelligence and travelled to Britain under an alias, investigative group Bellingcat reported Monday.
British authorities charged both last month under their assumed names, saying at the time they thought the Russian men were not who they said they were.
Bellingcat worked with Russian investigative group the Insider on their report.
Russian President Vladimir Putin, whose government has long denied having any knowledge of the attack, initially claimed that the two men's names "mean nothing to us", then said that they were civilians.
Bellingcat said he made multiple trips to Ukraine.
The two suspects gave a freaky interview to a Russian TV channel after the United Kingdom government released CCTV footage of their trip to Salisbury around the very time the Skripals were poisoned.
Russian Federation denies any involvement in the poisoning, and the two men have said publicly they were tourists who had flown to London for fun and visited Salisbury to see its cathedral.
The British website has scooped the rest of the media with its reports on the nerve agent attack that almost killed the ex-spy and his daughter in England, providing evidence the Russians had identities far more intriguing than the aliases they used as supposed tourists.
A spokesperson for London's Metropolitan Police said they would not comment on the "speculation".
Skripal, a Russian military intelligence officer turned double agent for Britain, and his visiting daughter spent weeks in critical condition after the Salisbury attack.
The two survived after a lengthy hospital stay in intensive care. The British woman, Dawn Sturgess, died after unwittingly spraying the novichok on her wrists.
The case prompted the biggest East-West diplomatic expulsions since the Cold War.
It revealed that Mishkin was born in 1979 in the small village of Loyga, north of Moscow.
His GRU rank was unknown, it added.
The website claimed Mishkin travelled extensively from 2011 to 2018 on a fake identity.
Until September 2014 his registered home address in Moscow was the same as the headquarters of the GRU.
The full report, presented by two Bellingcat reporters at Westminster on Tuesday, explained how they had pieced together evidence of the man's identity from scraps of information on the internet, via leaked official databases and using a copy of personal documents, including passport dossiers. Last week the U.S. Department of Justice indicted seven named GRU officers on charges they had hacked global organizations, including the Organization for the Prohibition of Chemical Weapons (OPCW).