Investigative website Bellingcat has identified the second suspect in the nerve-agent attack on former Russian spy Sergei Skripal in Britain as a military doctor employed by Russia's GRU military intelligence agency.
Last month, British prosecutors charged two Russians -- Ruslan Boshirov and Aleksandr Petrov -- with attempted murder for carrying out the poisoning of Skripal and his daughter, Yulia, with the Novichok nerve toxin in the southern English city earlier this year.
The prosecutors said at the time the two were undercover GRU officers.
Russia has repeatedly denied any involvement in the Skripals' attempted murder.
"We have now identified 'Aleksandr Petrov' to be in fact Dr. Aleksandr Yevgenyevich Mishkin, a trained military doctor in the employ of the GRU," the British-based group said in a report published on its website.
Bellingcat, a website that covers intelligence matters, had previously identified Boshirov on September 26 as being decorated GRU Colonel Anatoly Chepiga.
"While Aleksandr Mishkin's true persona has an even sparser digital footprint than Anatoly Chepiga's, Bellingcat has been able to establish certain key facts from his background," the October 8 report said.
It said that Mishkin was born in 1979 in the Archangelsk region in Northern European Russia and was trained as a military doctor for the Russian naval armed forces at one of Russia's elite military medical schools.
"During his medical studies, Mishkin was recruited by the GRU, and by 2010 had relocated to Moscow, where he received his undercover identity -- including a second national ID and travel passport -- under the alias Aleksandr Petrov," the report said.
"Bellingcat's identification process included multiple open sources, testimony from people familiar with the person, as well as copies of personally identifying documents, including a scanned copy of his passport," the website said.
In reaction to Bellingcat's latest report, British police said they would not comment on speculation regarding the real identities of those charged with poisoning the Skripals.
"We are not going to comment on speculation regarding their identities," London's police force said in a statement in response to a media query about the report.
Russian President Vladimir Putin has said that the two men shown in British surveillance footage near Skripal's home in Salisbury and identified by British authorities as Boshirov and Petrov were actually civilians on a tourist trip.
Skripal, a former GRU colonel, was convicted of treason in 2006 by a Russian court after being accused of spying for Britain. He relocated to Britain in a 2010 spy swap.
Putin on October 3 said that Skripal was a "scumbag" who had betrayed his country.
The Skripals were found unconscious on March 4 on a bench in the southern English town of Salisbury. They were seriously ill but made a full recovery after spending several weeks in a hospital.
British officials said the two were poisoned with Novichok, a military-grade chemical weapon that was developed in the Soviet Union, and blamed Putin's government for the attack.
In June, a British citizen, Dawn Sturgess, died and her boyfriend, Charlie Rowley, fell ill when they stumbled across remnants of the poison in a town near Salisbury.
Britain on September 5 announced charges against the two Russian men as police issued photographs of the suspects.
The men acknowledged they were in Salisbury at the time but claimed they were there as tourists.