London [UK], April 13 (ANI): Britain has alleged that Russia has indulged in the espionage of ex-Russian spy Sergei Skripal and his daughter Yulia for at least five years.

In a letter written to Nato Secretary General Jens Stoltenberg, Britain's National Security Adviser Sir Mark Sedwill has revealed that the Skirpals were the subject of "interest" from the Kremlin's security services since 2013, reported the Independent,

Sir Mark said: "We have information indicating Russian intelligence service interest in the Skripals, dating back at least as far as 2013, when e-mail accounts belonging to Yulia Skripal were targeted by GRU cyber specialists."

"We continue to judge that only Russia has the technical means, operational experience and motive for the attack on the Skripals and that it is highly likely that the Russian state was responsible. There is no plausible alternative explanation," he added.

According to the report, Sergei Skripal's daughter Yulia's email accounts had been targeted by cyber specialists which were associated with Russia's GRU intelligence agency.

Sergey Skripal was a former Russian military intelligence (GRU) officer, convicted of espionage in 2004.

"It is highly likely that the Russian intelligence services view at least some of its defectors as legitimate targets for assassination," Sir Mark said.

On a related note, the Organisation for the Prohibition of Chemical Weapons (OPCW) on Thursday backed Britain's findings that "high purity" Novichok was used to poisoning of ex-Russian spy Sergei Skripal and his daughter Yulia in the English city of Salisbury.

The Hague-based watchdog, without mentioning Novichok, in a statement says that its experts, "confirm the findings of the United Kingdom relating to the identity of the toxic chemical that was used in Salisbury and severely injured three people."

According to the British government, Skripal and his 33-year-old daughter Yulia were exposed to a military-grade nerve agent in the British city of Salisbury on March 4.

Yulia was able to recover from the attack after being hospitalised for over a week. She also gave her first public statement to media. She expressed her gratitude towards the people of Salisbury to offer emotional support to her and her family.

Skripal has been admitted to the Salisbury district hospital and has now been declared as out of danger.(ANI)

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