LONDON • Former Russian spy Sergei Skripal, who was poisoned with a nerve agent in Britain, triggering a diplomatic crisis with Russia, has been discharged from hospital, the facility said yesterday.

Nursing director Lorna Wilkinson at the Salisbury District Hospital said treating him and two others poisoned by the same nerve agent had been an "unprecedented challenge".

"This is an important stage in his recovery, which will now take place away from the hospital," she said.

Mr Skripal and his daughter Yulia, who was visiting from Moscow, collapsed on March 4 on a bench in Salisbury, the city in south-western England where the former double agent lives.

Police officer Nick Bailey who went to help them was also taken to hospital. He was discharged several weeks after the attack, while Ms Skripal was treated in hospital for just over a month.

"Treating people who are so acutely unwell, having been poisoned by nerve agents, requires stabilising them, keeping them alive until their bodies could produce more enzymes to replace those that had been poisoned," the hospital's statement said.

The poisoning sparked a diplomatic crisis that saw Russia and the West expelling dozens of diplomats.

Britain accused Russia of being behind the poisoning, saying it was caused by a type of nerve agent known as Novichok which was developed in the Soviet Union. A spokesman for British Prime Minister Theresa May, who called the attack a "reckless and despicable act", welcomed news of his discharge.

United Nations experts have confirmed that a high-purity nerve agent was used, without specifying whether it was Novichok or saying who might be behind the poisoning.

Russia has challenged Britain to provide evidence in the case and has requested consular access to the Skripals. But Britain's Foreign and Commonwealth Office said Ms Skripal had turned down Russia's offer of consular assistance.

Reacting to the news, Russian President Vladimir Putin said yesterday that Mr Skripal would be dead if a weapons grade agent had been used to poison him. He said, however, that Moscow was pleased to see Mr Skripal being discharged from hospital.

Britain's Metropolitan Police said it was making "good progress" in the case, noting that it was a "complex investigation". Both the Skripals are now likely to be in protective custody.

Mr Skripal is a former Russian military intelligence officer who passed information on Russia's agents in Europe to British security services, resulting in imprisonment in his homeland. He moved to Britain as part of a spy swop in 2010.

AGENCE FRANCE-PRESSE , REUTERS