LONDON - Britain has announced charges against two Russian men they believe poisoned former spy Sergei Skripal and his daughter Yulia with a deadly nerve agent, alleging they were military intelligence officers acting with approval from "a senior level of the Russian state."

In a statement on September 5, the Crown Prosecution Service (CPS) said that it was "clearly in the public interest to charge" the Russians, Aleksandr Petrov and Ruslan Boshirov, with crimes including attempted murder and the use of a chemical weapon .

Police issued photographs of the suspects, while Russia continued to deny involvement.

Prosecutors "have considered the evidence and have concluded there is sufficient evidence to provide a realistic prospect of conviction," it said.

The war of words with Russia following the Novichok attack has escalated, with a senior minister saying Vladimir Putin bore ultimate responsibility for the action of his spies.

The two men alleged to have been behind the March nerve agent poisoning – Alexander Petrov and Ruslan Boshirov – have been identified by the UK as members of the GRU, Russia's military intelligence service.

Security Minister Ben Wallace said Mr Putin had a strong grip over his state which "controls, funds and directs" the GRU.

British and Russian officials will come face-to-face as the UN Security Council discusses the attack in New York.

Prime Minister Theresa May told Parliament that based on the intelligence gathered so far, "the government has concluded that the two individuals named by the police and the CPS are officers from the Russian military intelligence service, also known as the GRU."

"This was also not a rogue operation. "It was almost certainly approved outside the GRU, at a senior level of the Russian state," May said.

The poisoning of Skripal, a former GRU officer, may have been meant "to give a message to those Russians who were living elsewhere who had been involved in matters relating to the Russian state," May said. "But it is up to the Russians to explain what happened in Salisbury."

Britain requested an urgent meeting of the UN Security Council in light of the charges, with British Ambassador Karen Pierce saying it would likely take place on September 6.

Meanwhile, Russian news media reported that Britain's ambassador to Russia, Laurie Bristow, met with Russian Foreign Ministry official Igor Neverov in Moscow to discuss the matter, without providing details.

A senior British police official, Neil Basu, called the charges "the most significant moment so far in what has been one of the most complex and intensive investigations we have undertaken in counterterrorism policing."

The CPS said that a European arrest warrant had been issued for the two Russians but that Britain would not seek their extradition, suggesting it would be fruitless to do so.

"We will not be applying to Russia for the extradition of these men as the Russian Constitution does not permit extradition of its own nationals," said Sue Hemming, director of legal services at the CPS.

Britain's Metropolitan Police said the men, both about 40, flew from Moscow to London on Russian passports two days before the Skripals were poisoned on March 4.

"It is likely that they were traveling under aliases and that these are not their real names," the police said, asking anyone who knows the suspects or saw them in Britain to contact the authorities.

Sergei Skripal, a former double agent who was sent west in a 2010 spy swap, and his daughter, Yulia, were found unconscious on a bench in the English city of Salisbury that afternoon.

They were both in critical condition and spent several weeks in the hospital, but were later released and "thankfully are now making a good recovery," Basu said.

British officials say they were poisoned with Novichok, a military-grade chemical weapon that was developed in the Soviet Union, and blamed Russian President Vladimir Putin's government for the attack.

Russia denies involvement, and a diplomatic dispute over the case has led to sanctions and the expulsion of more than 150 Russian diplomats from two dozen Western countries.

The poisoning has further damaged already severely strained relations between Russia and the West, and has been a cause for solidarity at a time when Western officials say Moscow is seeking to cause rifts in relations between Western countries.

Speaking ahead of the British announcement, Kremlin spokesman Dmitry Peskov again denied any Russian role in the poisoning, saying that Russia has no new information about it because Britain has refused to share case files.

Russian Foreign Ministry spokeswoman Maria Zakharova said on September 5 that the names and photographs released by British authorities "say nothing" to Moscow.

Russia's envoy to the world's chemical weapons watchdog, the Organization for the Prohibition of Chemical Weapons (OPCW), said that Moscow believes the British announcement was a "provocation."

"We said right away that Russia had nothing to do with the Salisbury incident," Aleksandr Shulgin told Russian state media.

British police detailed the movements of the two suspects and provided multiple CCTV images showing them at airports, train stations, and the streets of London and Salisbury.

According to police, the men arrived in London on an Aeroflot flight from Moscow on March 2. The following day, they took a train from London to Salisbury, where they spent less than two hours walking the streets before returning to London. Police said that trip to Salisbury was a reconnaissance of the city. On March 4, they left their London hotel in the morning and made another trip to Salisbury.

CCTV footage showed they were near Skripal's house and the police said they believe the two suspects contaminated the front door with Novichok. The suspects left Salisbury in the afternoon, returned to London, and flew back to Moscow on an Aeroflot flight shortly before the midnight on the same day.

In addition to conspiracy to murder Sergei Skripal, the Russians are charged with the attempted murder of Sergei and Yulia Skripal and Nick Bailey, a police officer who fell ill after going to Skripal's home after the attack; the use and possession of Novichok in violation of a British law on chemical weapons and toxic substances; and causing grievous bodily harm with intent to Yulia Skripal and to Bailey.

Sergei Skripal, 67, a former colonel in the GRU who also served in the Foreign Ministry, was convicted of treason in 2006 by a Russian court that found him guilty of spying for Britain. He was released from prison in 2010 and sent to the West in a high-profile Cold War-style spy exchange, and he lived in Salisbury at the time of the poisoning. His daughter Yulia, 34, was visiting from Russia.

On June 30, two people collapsed in a house in Amesbury, near Salisbury where the Skripals were poisoned with Novichok. Dawn Sturgess died in the hospital in July, while her partner, Charlie Rowley, later recovered. Police said they were exposed after handling what they believed to be perfume.

On September 4, the OPCW said laboratory tests showed that Sturgess's death was caused by the same substance that poisoned Skripal and his daughter.

However, it was not possible to conclude whether the nerve agent used in the May and June incidents was from the same batch, the OPCW said.

British police "have now linked the attack on the Skripals and the events in Amesbury which affected Dawn Sturgess and Charlie Rowley. It now forms one investigation," the September 5 police statement said. "We do not believe Dawn and Charlie were deliberately targeted, but became victims as a result of the recklessness in which such a toxic nerve agent was disposed of."

As a permanent member of the Security Council, Russia will be represented at Thursday's meeting – and called on by Britain to update members on progress in the Salisbury investigation – alongside UK allies such as the US and France.

Mrs May has been in contact with US President Donald Trump and other leaders as she attempts to build an international alliance in support of her stance.

The developments came amid claims that President Trump was "reluctant" to expel 60 Russian diplomats following the Salisbury poisonings in March.

An anonymous article in the New York Times, attributed to a "senior official in the Trump administration", claimed that the President "complained for weeks about senior staff members letting him get boxed into further confrontation with Russia ... But his national security team knew better — such actions had to be taken, to hold Moscow accountable".

Washington was gripped by speculation over the author of the column, which painted a damning portrait of the President's "amorality" and his "impetuous, adversarial, petty and ineffective" leadership style, and claimed that many members of his own administration were secretly working to rein him in.

President Trump himself suggested in a series of angry tweets that the anonymous official may have committed treason, or may even be fictitious.

Australia on Thursday said it was in "lock step" with the UK on the importance of holding Russia to account over the "heinous" attack, although it is not currently a council member.

Former GRU officer Sergei Skripal and his daughter Yulia were left critically ill after being exposed to the military grade nerve agent Novichok in March.

The alleged perpetrators were identified in a dramatic joint police and Crown Prosecution Service press conference.

Detectives believe it is likely the pair, thought to be aged around 40, travelled under aliases and that Petrov and Boshirov are not their real names.

Prosecutors deem it futile to apply to Russia for the extradition of the two men, but a European Arrest Warrant has been obtained and the authorities are also seeking the assistance of Interpol.

Detectives believe the front door of Mr Skripal's Salisbury home was contaminated with Novichok on March 4.

Mr Skripal, 67, and his daughter were found unconscious on a bench in Salisbury city centre the same day and spent weeks critically ill in hospital.

Metropolitan Police Assistant Commissioner Neil Basu also confirmed officers have now linked the attack on the Skripals to events in nearby Amesbury four months later.

In the second incident, Dawn Sturgess, 44, and her partner Charlie Rowley, 45, were exposed to the same nerve agent used in Salisbury.

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

In a statement, the Russian Embassy in the UK accused the British authorities of being unwilling to engage with them and called on the Government to "give up politicised public accusations".