Russia won't take on faith any conclusion relating to the Skripal affair until such a time as Russian experts are allowed access to the samples mentioned.
While her whereabouts are unknown, Skripal said she is being supported by police officers who are keeping her informed of their high-profile investigation.
Yulia Skripal, the daughter of former Russian spy Sergei Skripal who was poisoned in March, has turned down an offer of help from the Russian Embassy, according to police.
We will not let the current attack, or any new anti-Russian attack, go without a tough response, Russia's foreign ministry said in a statement.
Britain blames Russia for the March 4 poisoning of former double agent Sergei Skripal and his daughter Yulia, a charge the Kremlin furiously denies.
Dozens of US diplomats and their families left the embassy compound on three buses and a minibus that headed towards the airport, after Moscow set a Thursday deadline for the envoys to leave Russia.
The samples were collected from Sergei Skripal and his daughter, Yulia, who have been hospitalised since when they were found on a public bench in the English city of Salisbury in early March.
Putin urged 'common sense' to prevail in the spy poisoning crisis as London and Moscow faced off in a tense meeting at the world's chemical weapons watchdog.
head of Russia's SVR foreign intelligence agency said Wednesday the poisoning of Russian former spy Sergei Skripal in Britain was a "grotesque provocation" by the UK and US.
Russia has ordered 50 more British diplomats to leave the country, after a former Russian spy and his daughter were poisoned with a military grade nerve agent on British soil.
Russia's mass expulsion of US diplomats Thursday is the latest tit-for-tat move triggered by the poisoning of a Russian former double agent in England.
Describing them as "intelligence officers", US ordered closure of the country's consulate in Seattle over the use of nerve agent allegedly by Moscow against a former Russian spy in the UK.
The crisis erupted after Sergei Skripal and his daughter Yulia were exposed to a Soviet-designed nerve agent on March 4, leaving them in critical condition.
Russia set to re-elect Vladimir Putin as President amid allegations of ex-spy poisoning, election meddling
Putin, who has ruled Russia for almost two decades, is polling at around 70 percent and is sure to extend his term to 2024 despite a lacklustre campaign.
Given international conventions that prohibit the use of chemical weapons, research conducted at Porton Down is defensive in nature, according to the defence ministry.