British prosecutors said Wednesday they have obtained a European arrest warrant for two Russians blamed for a nerve agent attack on a former spy in the city of Salisbury.
Police identified Alexander Petrov and Ruslan Boshirov as the men who tried to kill Russian former double agent Sergei Skripal and his daughter Yulia with Novichok in March.
The Crown Prosecution Service (CPS) said it would not apply for their extradition, as Russia had made clear in previous cases that it did not extradite its nationals.
"We have, however, obtained a European arrest warrant," said CPS director of legal services, Sue Hemming.
"[This] means that if either man travels to a country where an EAW is valid, they will be arrested and face extradition on these charges for which there is no statute of limitations."
Assistant Commissioner Neil Basu of London's Metropolitan Police, Britain's top counter-terrorism officer, said the two men were believed to be in their 40s.
"It is likely that they were travelling under aliases and that these are not their real names," he said.
Basu added that photos were being released of the men in the hope that a member of the public would recognise them.
The CPS said the pair faced charges of conspiracy to murder Skripal, and the attempted murder of him, his daughter and Nick Bailey, a policeman injured in the attack.
They are also accused of using a banned chemical weapon and causing grievous bodily harm with intent to Yulia Skripal and Bailey.
Skripal was a colonel in Russian military intelligence who was jailed for betraying agents to Britain's MI6 security service. He moved to England in 2010 as part of a spy swap.
The nerve agent was believed to have been smeared on the front door of his house in the sleepy southwestern English city of Salisbury.
- Diplomatic expulsions -
London blamed the Russian state for the attack, but Moscow strongly denied any involvement.
The incident sparked a diplomatic row that led to tit-for-tat diplomatic expulsions between Britain and its allies and Russia, while the United States also imposed sanctions.
The Skripals and Bailey both recovered, but on June 30, a British couple fell ill from the same type of nerve agent in the nearby town of Amesbury.
One of them, 44-year-old mother of three Dawn Sturgess, died on July 8.
Her partner Charlie Rowley was discharged, although he later went back to hospital and is currently being treated for meningitis and loss of eyesight.
The Organisation for the Prohibition of Chemical Weapons (OPCW), a global watchdog, on Tuesday confirmed that Novichok was involved in their poisoning.
Police said Wednesday that their case is now part of the Skirpal investigation.
"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," Basu added.
Novichok is a military-grade nerve agent developed by the Soviet Union during the Cold War.