London: Sergei V. Skripal, the former Russian spy whose poisoning in a sleepy English city touched off a diplomatic storm between Russia and the West, has been released from a hospital, British officials said on Friday.

Skripal, 66, and his daughter, Yulia, were both in critical condition after they were poisoned with a nerve agent known as a novichok - developed by Soviet scientists for battlefield use against Western troops - in the cathedral city of Salisbury, in southwest England, on March 4.

The British authorities said that Russia was to blame for the attack, an accusation that significantly raised tensions between the two countries and led to the expulsion of hundreds of diplomats from Britain, its allies and Russia.

"It is fantastic news that Sergei Skripal is well enough to leave Salisbury District Hospital," Cara Charles-Barks, chief executive of the hospital, said in a statement.

Shortly after the poisoning, both victims were put into induced comas, a technique that lowers metabolism and may prevent poison from damaging the organs. They were also given medication to suppress seizures and an antidote, like atropine

Early reports suggested that the Skripals were hovering between life and death, and a court order issued in late March suggested that one or both may have sustained severe brain damage.

But about a week later, to the surprise of many, the police announced that Yulia Skripal had regained consciousness.

She was released from the hospital in early April. The prognosis for both Skripals has continued to improve.

The attack may have gone awry because of the "substrate" that was mixed with the nerve agent in order to get it to stick to the victims' skin, said Richard Guthrie, a chemical weapons expert formerly of the Stockholm International Peace Research Institute.

The police have suggested that the nerve agent was in liquid form, and that the Skripals were exposed at Skripal's front door.