Suspects in Novichok case flew out of UK in wake of attack, source says

The pair left the UK in the wake of the attack on what is believed to have been a commercial flight, the source added.

Their departure was revealed in a coded Russian message to Moscow sent after the attack, which was intercepted by a British base in Cyprus, the source said. The British government blames the Skripals' poisoning on Russia.

The suspects were identified by UK police, who have been combing through months of surveillance camera footage from UK airports and from Salisbury, the town where the Skripals were poisoned on March 4.

Using facial recognition technology, authorities discovered two "fresh identities" -- individuals not known to have been spies or used in other attacks -- the source added.

Investigators crosschecked that information with the manifest of the flight on which the suspects were believed to have left Britain. They traveled on aliases, the source said.

An Aeroflot flight at Heathrow airport in London was searched on March 30, an action the British government described at the time as "routine."

Russia's Ambassador to the United Kingdom Alexander Yakovenko shrugged off the claims at a Russian Foreign Ministry event in Moscow on Thursday. "These are the reports of the media," he told reporters. "Unfortunately, we don't have official statements from the British side. I want to hear from Scotland Yard or the Foreign Office. A lot of versions have been appearing in the newspapers, they are not supported by the statements of the Foreign Office," he said.

The British Foreign Office declined to comment, directing CNN to the police. London's Metropolitan Police, which is leading the investigation into the Skripals, declined to comment.

Britain's Press Association news agency also reported Thursday that police had identified suspects in the case.

The attack on the Skripals led to a diplomatic dispute with Russia. The UK expelled 23 Russian diplomats and more than 20 other countries, including the United States, followed suit.

Russia has repeatedly denied any involvement in the attack and has put forward multiple theories as to who may have been behind it.

The Skripals were found unconscious on a bench in the city of Salisbury on March 4. They were treated for exposure to the rare Soviet-era military-grade nerve agent Novichok and discharged separately from hospital several weeks later. Police believe they came into contact with the substance via the door handle of Sergei Skripal's house.

Tensions escalated further earlier this month when two British residents of Amesbury, a town eight miles north of Salisbury, fell ill after being exposed to the same nerve agent. Dawn Sturgess, 44, later died, while her partner Charlie Rowley, 45, remains in hospital.

Although police said there was no suggestion that the couple had been deliberately targeted, a murder investigation was launched. Last week, police announced that they had identified a small bottle found in Rowley's home as the source of the nerve agent that killed his partner.

It is unclear where Rowley found the bottle, or whether it is the same batch of nerve agent that poisoned the Skripals.