A British health official said Tuesday that Yulia Skripal, who was targeted along with her father in a nerve agent attack in England, has been discharged from hospital.
"This is not the end of her treatment but marks a significant milestone," said Dr. Christine Blanshard.
She said she would not provide details about Skripal's condition out of concern for the patient's privacy.
The 33-year-old daughter of ex-spy Sergei Skripal, 66, has been taken to a secure location.
Blanshard said Sergei Skripal, the apparent target of the attack, is recovering more slowly than his daughter but continues to improve.
The doctor said no date has been set for the elder Skripal's release from Salisbury District Hospital.
The two were poisoned March 4 in an attack that has led to a prolonged confrontation between Russia and Britain that has revived Cold War tensions.
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The British government is likely to keep details about Yulia Skripal's location secret given the sensitivity of the case.
If she is well enough, she is likely to be extensively questioned by British security officials and police about her recollection of events leading up to her poisoning, which sparked a major confrontation between Britain and Russia that recalls Cold War tensions.
Yulia Skripal was in critical condition after the attack.
She had arrived in England on an Easter visit from Moscow the day before the attack.
Sergei Skripal is a former Russian military intelligence officer who was convicted in Russia of spying for Britain.
He was imprisoned in Russia and eventually settled in England after a "spy swap."
Britain has accused the Russian government of masterminding the attack on the Skripals, who were found unconscious on a bench in the English city of Salisbury.
British officials say Russia had the means and the motive to attack Sergei Skripal, who was convicted of betraying Russia.
The British government maintains the Skripals were poisoned by a military-grade nerve agent that could only have been made in Russia. Russia has denied the allegation.
The incident has led to a mass expulsion of Russian diplomats from countries aligned with Britain. Russia in turn retaliated by expelling diplomats from a number of countries that have sided with Britain.