Police said the perfume bottle contained significant amounts of Novichok and they believe it had been left behind by the two suspects after the Skripal attack. Russia's foreign ministry said the names given by Britain did not mean anything to them.
British police released CCTV images of two Russian men they said flew in to Britain for a weekend to commit murder.
Hemming said Britain would not apply to Russian Federation to extradite the men because the Russia's constitution does not allow the extradition of its own nationals. The two men can still be arrested in the unlikely event that they travel to another European country.
"What we have learned today is the specific threat from GRU", May said.
Sergei Skripal, 67, is a former colonel in the GRU who was convicted in 2006 of spying for Britain and imprisoned. Russian authorities ultimately discovered and arrested Skripal, who was then traded to the Americans in a high-profile spy swap. They spent weeks in hospital in critical condition before Yulia being released in April and Sergei in May.
Police are also still gathering information about the poisonings.
British prosecutors announced the new development Wednesday.
The poisoning ignited a diplomatic confrontation in which hundreds of envoys were expelled by both Russian Federation and Western nations.
Police on Wednesday gave new details about what Basu called "one of the most complex investigations" the force had ever seen.
Having taken advice from Public Health England, police say they are confident that there was no risk to members of the public who were on the same flight, trains or public transport used by the suspects.
Police said the two men then applied the poison to Skripal's door and flew back to Russian Federation just hours later.
Officers did not search their room until May 4 - two months after the Skripals were discovered unconscious on a park bench in Salisbury - but when they did, they found traces of Novichok. The police believe that the front door was contaminated by the nerve agent, following which the suspects returned to Heathrow airport and flew back home.
That confirms a statement made by Charlie Rowley, who said that in July he had found what he thought was a bottle of perfume, which he had given to his partner Dawn Sturgess who later died from the effects of Novichok.
The men will also be charged with possession of novichok, a deadly Soviet-era poison that's banned by the Chemical Weapons Act.
Basu told reporters that the March 4 poisoning of the Skripals had now been formally linked by United Kingdom investigators to the June 30 poisoning of Dawn Sturgess and Charlie Rowley, a couple living in Amesbury, near Salisbury.
The Skripal case has increased tension between the West and Russian Federation, and led to a flurry of sanctions and diplomatic expulsions.
A British inquiry in 2016 concluded that Russian President Vladimir Putin probably approved Litvinenko's murder, an accusation that Moscow has always rejected.
Later they confirm that the man and woman had come into contact with Novichok.
Although another spy agency, the SVR, is Russia's official foreign intelligence service, the GRU is mandated to undertake operations around the world.
Russian Federation must rein in the activities of its military intelligence officers and account for their actions, May said.