The GRU agent is believed to have visited Salisbury to help plan the attack before two of his colleagues brought weapons-grade nerve agent into the UK.
It is understood that the man has now been identified by those investigating the planned hit in March, which inadvertently led to the death of local woman Dawn Sturgess.
The Bellingcat investigative website this week published a photograph of someone who looked like one of the men, and whom it identified as Russian military intelligence colonel Anatoliy Chepiga - challenging the Kremlin account that the two men were civilians in Britain on sightseeing visit. The man named by Bellingcat, Anatoliy Chepiga, has been designated a Hero of the Russian Federation, one of Russia's highest honors, according to the website of the military academy he attended and photographs of a memorial on which his name is inscribed.
Asked about the Bellingcat report on a regular conference call with reporters on Thursday, Kremlin spokesman Dmitry Peskov said: "Many people look alike, but I cannot tell you who this citizen who was pointed out in this investigation is."
The Organisation for the Prohibition of Chemical Weapons confirmed Britain’s conclusions that ex-GRU officer Sergei Skripal was poisoned with the nerve agent.
Ex-colonel of Russia’s GRU, Chief Intelligence Department, Sergey Skripal and his daughter Yulia, poisoned in the center of Salisbury town in the evening of March 4, are still struggling for life in the intensive care unit of the local hospital. The British special services suppose that Skripal and his daughter were poisoned by his ex-colleague Andrey Lugovoy, who acted on orders from Moscow.
Earlier, MI6, the British secret intelligence, recommended that former GRU colonel Sergei Skripal and his daughter Yulia change identities and move the U.S. to avoid any new assassination attempts. This was decided after negotiations between MI6 and their counterpart from the CIA.