One of Russia's top law officials has been killed in a mysterious helicopter crash, followed by claims that he had been leaking confidential information to the West, including Britain.

Deputy prosecutor-general Saak Karapetyan - a former MP and long-time ally of President Vladimir Putin - died last night when his AS-350 came down in Kostroma region northeast of Moscow.

His death came just hours before four Russian intelligence officers were outed by the Dutch government as having tried to hack the global chemical weapons watchdog OPCW in The Hague in April, shortly after the Novichok attack in Salisbury, UK.

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Deputy prosecutor-general Saak Karapetyan - a former MP and long-time ally of President Vladimir Putin - died in a helicopter crash

Coincidentally, Karapetyan had been in charge of the Russian criminal investigations into the poisoning of former spy Sergei Skripal and his daughter Yulia in March.

He also led the investigation into the deaths of Putin foe Boris Berezovsky, and dissident Alexander Litvinenko - which both took place on UK soil.

It has today been claimed that 'his death will resolve a number of very painful issues' in the Russian government.

An anonymous insider posted on a channel on the popular Telegram messaging app called NeZygar that Karapetyan's death 'will stop leaks of highly confidential information to the West'.

The insider claimed it would specifically prevent leaks to the secret services of Britain, the US and Switzerland, and stop attacks on Putin's security council chief Nikolai Patrushev.

Karapetyan was one of three people who died when the AS-350 helicopter came down in Kostroma region northeast of Moscow last night

Mystery: The cause for the crash is not yet know, but Russian media reports the pilot - who also died in the crash - was 'highly experienced'

No survivors: The charred remains of the wreckage can be seen in official images

Claims: An anonymous 'Kremlin insider' has posted on a popular Telegram channel that Karapetyan had been leaking information to Western powers, including the UK

No further details were given on the explosive claim.

NeZygar, a 'blog channel' has 93,000 subscribers and has previously proven to be a well informed insider.

Karapetyan was one of three people who died in the crash some 65 miles north east of Moscow last night.

The pilot who died, named as Stanislav Mikhnov, 54, was described as highly experienced in Russian media.

'The wreckage of the helicopter was found near the village of Vonyshevo, the aircraft was burned,' added an emergencies ministry source cited by Tass.

'The debris of the crashed helicopter have been found. Three people died in that crash.

'Their bodies were also found at the crash site,' the source said.

Deputy prosecutor-general Saak Karapetyan, 58, had been in charge of the Russian criminal investigation into the poisoning of Sergei Skripal in Salisbury, UK, earlier this year

Dutch authorities have released images of four Russian agents who tried to hack into the global chemical weapons watchdog a month after the Salisbury novichok attack. CCTV shows them when they were kicked out of the Netherlands

The Investigative Committee has launched a criminal probe into the helicopter crash, it was announced.

In April, Karapetyan had blasted Theresa May's government over the Skripal poisoning.

He said: 'The British authorities have based the anti-Russian campaign surrounding the poisoning of former GRU officer Skripal and his daughter on a provocative scenario.

'A similar scenario was used in baseless allegations of Russia's attempt on the life of Boris Berezovsky in London in summer 2003 and the circumstances surrounding the death of Alexander Litvinenko in the UK in November 2006.

'I should say that the targets of those three provocations were persons charged with grave felonies in Russia who repeatedly made statements criticising the Russian authorities.

'A false motive for their physical liquidation was thus created.'