U.K. Police Charge 3rd Man in Effort to Kill Russian Dissident

British counterterrorism police announced criminal charges against a senior Russian military intelligence officer on Tuesday for the attempted assassination of a former Russian spy who was poisoned in England in 2018 with a deadly nerve agent.

Breaking with past practice, the police identified the officer by his real name, Denis Sergeev, instead of the alias he used to enter the United Kingdom on March 2, 2018. That was two days before the former Russian spy, Sergei V. Skripal, and his daughter Yulia collapsed on a park bench in the English town of Salisbury.

Mr. Sergeev is the third officer to be charged in the poisoning of Mr. Skripal. Months after the poisoning, British authorities charged two officers, identified by the aliases Ruslan Boshirov and Aleksandr Petrov, with carrying out the attack by applying the nerve agent, known as Novichok, to the doorknob at Mr. Skripal’s home in Salisbury. All three are members of Unit 29155, a division within Russia’s military intelligence agency, known as the G.R.U., that specializes in sabotage and assassination.

“We will not let this go,” Priti Patel, the British home secretary, said in a statement to Parliament on Tuesday, describing the poisoning as “an appalling event that shook the entire country and united our allies in condemnation.”

The charges in the Skripal case came on the same day that the European Court of Human Rights ruled that Russia was responsible for the 2006 killing of another former intelligence officer, Alexander V. Litvinenko, who was poisoned when Russian operatives put a radioactive isotope in his tea at a London hotel.

While Russia has repeatedly denied involvement, both poisonings have come to define Moscow’s relationship with the West. The first awoke the Western security establishment to the recklessness of Russian spycraft under President Vladimir V. Putin, while the second showed that such covert actions had become Kremlin policy, touching off a Cold War-style confrontation that is still reverberating.

In both cases, the motivation for the attacks appeared to be revenge, a driving force behind many Russian intelligence operations abroad, according to Western security experts. Mr. Litvinenko, a former operative in Russia’s domestic intelligence service, the F.S.B., fled to London after blowing the whistle on what he described as corruption and criminality in the service when it was overseen by Mr. Putin before he became president in 2000.

Mr. Skripal arrived in England in 2010 after a spy swap between the United States and Russia. He had been recruited by British intelligence while stationed as a G.R.U. officer in Spain in the 1990s and was arrested for espionage in 2006 in Moscow.

Both former spies continued to consult with intelligence agencies from countries the Kremlin views as adversaries, a possible reason they were targeted for assassination.

Tuesday’s announcement marks the first public acknowledgment of Mr. Sergeev’s role in the poisoning, though the investigative journalism collective Bellingcat first reported his involvement in February 2019. Using the alias Sergei Fedotov, Mr. Sergeev has been involved in violent operations across Europe, including the attempted poisoning of an arms merchant in Bulgaria, Western intelligence services say. The authorities in Spain say he flew to Barcelona just days before a 2017 referendum on independence in Catalonia, though it is still not clear whether he had any connection with the violent protests in the referendum’s aftermath.

(The Novichok nerve agent used on Mr. Skripal was also used last year to poison Aleksei A. Navalny, Mr. Putin’s most visible critic, who was imprisoned in March after returning to Russia from Germany, where he had gone for medical treatment. But Western intelligence services say it was the F.S.B., the domestic intelligence service, and not the G.R.U. that carried out that attack.)

Western security officials, speaking on condition of anonymity, have long described Mr. Sergeev as the senior officer in charge of coordinating the Skripal operation from London, but a statement by the British counterterrorism police on Tuesday offered more details.

In the statement, the police said that Mr. Sergeev met more than once in London with the officers using the names Petrov and Boshirov, whom Bellingcat later identified as Anatoly Chepiga and Aleksandr Mishkin. Tests carried out at the central London hotel where Mr. Sergeev stayed found no traces of the Novichok nerve agent, unlike at the hotel where the other operatives stayed.

Dean Haydon, assistant commissioner of the Metropolitan Police and senior national coordinator for counterterrorism policing, told reporters that “the three operated as a small team with a view to deploying Novichok to kill individuals in this country.”

“I can prove they were here operating as a unit linked to the G.R.U.,” he said. “We remain as determined as ever to bring those responsible to justice.”

Mr. Sergeev was charged with conspiracy to murder, attempted murder and possession and use of a chemical weapon. The three suspects are in Russia, and there is little chance anyone involved in the poisonings of Mr. Skripal and Mr. Litvinenko will face trial.

In addition to Mr. Skripal and his daughter, a British police officer, Detective Sergeant Nick Bailey, who was among the first to respond to Mr. Skripal’s home, was also poisoned. All three survived, but a 44-year-old mother of three, Dawn Sturgess, later died when she sprayed herself with the contents of a perfume bottle that police later said was used to transport the nerve agent. Her boyfriend, who was also sickened and survived, had found the bottle, disguised to look like Nina Ricci Premier Jour perfume, in a garbage bin.

The new charges came on the same day that the European Court of Human Rights concluded that Mr. Litvinenko’s assassins in 2006 were acting as “agents of the Russian state.” The ruling bolstered a separate inquiry by Britain that found “strong circumstantial evidence” that Mr. Putin and his spy chief at the time, Nikolai Patrushev, had approved an operation to kill Mr. Litvinenko, using a dangerous and rare isotope, polonium 210.

The lengthy British inquiry concluded in 2016 that Andrei K. Lugovoi, a former K.G.B. bodyguard, and Dmitri V. Kovtun, a Red Army deserter, poisoned Mr. Litvinenko.

While the 328-page report was scathing, it cited no specific evidence that Mr. Putin or Mr. Patrushev had been aware of the plot to kill Mr. Litvinenko or had sanctioned it.

Russian authorities have been openly disdainful of claims that Russian intelligence operatives were involved in the poisonings. In 2018, after British authorities charged Mr. Chepiga and Mr. Mishkin and described their roles in the Skripal poisoning, the pair gave an interview to one of the Kremlin’s chief propagandists, claiming implausibly that they were tourists and hinting that they were in fact in a romantic relationship.

Mr. Lugovoi, meanwhile, was given a seat in Russia’s rubber-stamp Parliament, which guarantees him immunity from prosecution at home. On Tuesday, Mr. Lugovoi told the Russian newswire Interfax that the European Court ruling was “wrongful, unlawful and politically biased.”

Michael Schwirtz reported from Kyiv, and Cora Engelbrecht from London. Marc Santora contributed reporting from London, and Anton Troianovski from Moscow.