One of the prime suspects in the Salisbury nerve agent attack is a highly decorated Russian military colonel, an online investigative group has claimed.

Bellingcat reported that the man who was named as Ruslan Boshirov and said by the Kremlin to be a civilian is actually Colonel Anatoliy Chepiga, a top-level officer in the GRU, Russia’s military intelligence service.

The Home Office said it could neither confirm nor deny the reporting about the suspect’s real identity.

But Defence Secretary Gavin Williamson briefly appeared to confirm the story, posting and then deleting a tweet that said: “The true identity of one of the Salisbury suspects has been revealed to be a Russian Colonel. I want to thank all the people who are working so tirelessly on this case.”

The Ministry of Defence said Mr Williamson’s social media profile was personal and it did not know why the tweet was deleted. Scotland Yard declined to comment.

Prime Minister Theresa May also referenced the Salisbury attack during an address to the United Nations General Assembly on Wednesday, saying: “We have seen what happens when the natural patriotism which is a cornerstone of a healthy society is warped into aggressive nationalism, exploiting fear and uncertainty to promote identity politics at home and belligerent confrontation abroad, while breaking rules and undermining institutions.

“And we see this when states like Russia flagrantly breach international norms – from the seizing of sovereign territory to the reckless use of chemical weapons on the streets of Britain by agents of the Russian GRU.”

Prime Minister Theresa May
Prime Minister Theresa May addresses the United Nations General Assembly (Richard Drew/AP)

The report threatens to undermine Vladimir Putin’s publicly held position that the two suspects had been identified by authorities as Russian civilians. Moscow did not immediately comment.

Bellingcat claimed it pieced together the identity after trawling online records from Russian military training academies, where they found a photo of a soldier that resembled Boshirov.

The academy website said the man received the Hero of the Russian Federation award – a decoration reportedly handed out by Mr Putin himself.

Further digging by Bellingcat threw up Colonel Chepiga’s name as linked to Chechnya, where the photo was taken, the academy mentioned and the award.

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Anatoliy Chepiga’s passport photo from 2003 (Bellingcat)

Two sources provided its journalists with passport photos – one under the name Anatoliy Chepiga from around 2003 and one under the name Ruslan Borishov from 2009.

Chepiga was born on April 5 1978 and graduated into the military following a stint at one of Russia’s elite training grounds, the report said.

His military career reportedly took him into the second Chechen war as part of a unit that played a “key role” in the conflict.

Earlier this month, Britain accused Russia of “lies and blatant fabrications” after the prime suspects in the Novichok attack claimed they visited the UK as tourists.

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Salisbury suspects Alexander Petrov and Ruslan Boshirov (Met Police)

The men, who said their names were Alexander Petrov and Ruslan Boshirov, told Russian state-funded news channel RT they travelled to the “wonderful” city in Wiltshire after recommendations from friends.

The pair claimed they have been left fearing for their lives after Britain pointed to their involvement and said they were officers in Russian military intelligence service the GRU.

Downing Street called the content of the interview “deeply offensive to the victims and loved ones of this horrific attack”.

In a translation from Russian, the pair told RT editor-in-chief Margarita Simonyan they worked in the fitness industry.

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‘Ruslan Boshirov’ and ‘Alexander Petrov’ on Fisherton Road, Salisbury (Metropolitan Police/PA)

Mr Putin said the men had been discounted as members of his security network, and insisted they were civilians.

UK authorities believe the pair smeared the highly toxic Novichok chemical on a door handle at the Wiltshire home of former GRU officer Sergei Skripal, leaving Mr Skripal and his daughter Yulia critically ill on March 4.

On June 30, in nearby Amesbury, Dawn Sturgess, 44, and her partner Charlie Rowley, 45, were exposed to the same nerve agent.

Ms Sturgess died in hospital in July, just over a week after the pair fell ill.

A police officer who visited the home of the Skripals shortly after the attack, Nick Bailey, was also left critically ill from exposure to the substance.