Britain on Tuesday warned three Russian intelligence officers wanted for a 2018 Novichok attack on a former double agent in the English city of Salisbury that they face arrest and prosecution if they ever leave their home country.

Home Secretary Priti Patel said Britain "will not tolerate such malign activity" and said it had applied for an Interpol notice to detain and extradite all three from abroad if given the chance.

"Should any of these individuals ever travel outside Russia, we will work with our international partners to take every possible step to detain them and face justice," she told parliament.

Prosecutors said there is enough evidence to charge Sergey Fedotov with the Skripal attack
Prosecutors said there is enough evidence to charge Sergey Fedotov with the Skripal attack Metropolitan Police / -

Patel's warning came after prosecutors said there was enough evidence to charge a third Russian man with the attack on Sergei Skripal and his daughter Yulia.

Counter-terrorism detectives said it was "clearly in the public interest" to charge Denis Sergeev with conspiracy to murder, attempted murder, causing grievous bodily harm, and possession and use of a chemical weapon.

Skripal and his daughter were left fighting for their lives after the attack in March 2018 while a police officer investigating the case fell seriously ill and a local woman who came into contact with the nerve agent later died.

Fedotov, also known as Denis Sergeev, was linked to an attempted poisoning in Bulgaria
Fedotov, also known as Denis Sergeev, was linked to an attempted poisoning in Bulgaria Metropolitan Police / -

The incident soured diplomatic ties between Britain and Russia that were already strained by the 2006 radiation poisoning of Alexander Litvinenko.

The announcement of a third suspect came as Europe's top rights court on Tuesday ruled that Russia was responsible for the murder of Litvinenko, a dissident former agent who accused President Vladimir Putin before his death.

Moscow rejected the court's claim as well as renewed British allegations the Kremlin was behind the Skripal attack -- the first offensive use of chemical weapons in Europe since World War II.

Ruslan Boshirov and Alexander Petrov -- also known as Anatoly Chepiga and Alexander Mishkin -- were previously declared wanted by British police
Ruslan Boshirov and Alexander Petrov -- also known as Anatoly Chepiga and Alexander Mishkin -- were previously declared wanted by British police Metropolitan Police Service / HO

"We resolutely condemn all attempts by London to shift responsibility onto Moscow," said Foreign Ministry spokeswoman Maria Zakharova.

The attack on the Skripals was the first offensive use of chemical weapons in Europe since World War II
The attack on the Skripals was the first offensive use of chemical weapons in Europe since World War II AFP / Daniel LEAL-OLIVAS

The UK had previously identified two suspects in the Skripal poisoning and issued European arrest warrants against them: Anatoly Chepiga and Alexander Mishkin.

Chepiga, Mishkin and Sergeev are members of Russia's GRU military intelligence service, police said.

Using the alias Sergey Fedotov, Sergeev travelled to London shortly before the other two and met them on several occasions between March 2 and 4, 2018, police said.

The attack on the Skripals was the first offensive use of chemical weapons in Europe since World War II
The attack on the Skripals was the first offensive use of chemical weapons in Europe since World War II AFP / Daniel LEAL-OLIVAS

British media reported that Sergeev has a higher rank than the others and may have led the operation. Police said no traces of Novichok were found in his hotel room.

Britain has not requested Sergeev be handed over, as Russia does not allow the extradition of its nationals.

Detectives said they had found evidence that three men "also previously worked together, for the GRU, as part of operations outside of Russia".

The British-based investigative group Bellingcat previously linked a Russian GRU officer named Denis Sergeev both to the attack on the Skripals and to an attempted poisoning in Bulgaria.

Sofia later charged a Russian of the same name.

In February 2019, the media outlet reported that a third Russian military intelligence officer was in the UK at the same time as the other two suspects, naming him as Denis Sergeev, a high-ranking GRU officer.

"The involvement of a GRU major general would indicate the unusually high importance of the operation," Bellingcat wrote in its joint analysis with the BBC.

The BBC found Sergeev used messaging apps such as WhatsApp and Telegram to communicate with the two Russians in Salisbury and his Moscow commander.

Bellingcat said Sergeev's Moscow contact was using an unregistered mobile phone card that "does not produce the regular 'footprint' left by regular numbers".

Bellingcat in 2019 said that Sergeev may also have been involved in an attempted poisoning in Bulgaria in 2015 of Emiliyan Gebrev, an arms manufacturer.

It said Sergeev travelled from Sofia to Istanbul and then on to Moscow in the evening of the day Gebrev was poisoned.

Bulgaria in 2020 charged three Russians in their absence with attempted murder of Gebrev, his son and his company manager.

Sofia City Prosecutor's Office named one as Sergey Fedotov, born in 1973, and also known as Denis Sergeev.