The head of Russian military intelligence, the organisation accused of being behind the Salisbury novichok poisonings, has died.

General Colonel Igor Korobov had been in charge of the GRU since 2016, the culmination of a 33-year career in military intelligence.

His death at the age of 63 was revealed by a Russian defence ministry source to the state-backed news agency Tass.

It said that he had died after a “serious illness”.

“The leadership of the Defence Ministry of the Russian Federation, General Staff of the Armed Forces of the Russian Federation (GSA) and Main Directorate of the General Staff of the Armed Forces of the Russian Federation inform with great sadness that on 21 November 2018, after a serious and long illness, head of the (GRU), deputy chief of the GSA Colonel General Korobov Igor Valentinovich passed away at the age of 63,” a statement said.

“The memory of a wonderful person, a true son of Russia, a patriot of the Fatherland Colonel General Korobov Igor Valentinovich will forever remain in our hearts. We express condolences to his family and friends.”

It is not the first time the organisation’s chief has died in the job – Korobov’s predecessor Igor Sergun died suddenly in January 2016 in circumstances described as “unclear”.

His death came three weeks after he was sent to Syria by Russian president Vladimir Putin to demand the Syrian president step down.

Lebanese newspaper al-Akhbar quoted a London-based diplomatic source as saying Mr Sergun was killed in a secret mission that several Arab and Middle Eastern intelligence agencies took part in.

The source hinted that he had been assassinated but Russian presidential press secretary Dmitry Peskov responded to this by saying: “We have already voiced everything we could.”

In March this year two GRU operatives flew into the UK in what the UK government has said was a mission to assassinate double agent and former GRU colonel Sergei Skripal.

Russia denies the allegations.

Alexander Mishkin and Anatoliy Chepiga are accused of smearing the nerve agent novichok on the door handle of Mr Skripal’s Salisbury home.

He and his daughter Yulia were taken seriously ill, as was a police officer who went to their aid after they collapsed in the city. All three eventually recovered from being poisoned.

A major operation took place to decontaminate the centre of Salisbury, but in July locals Charlie Rowley and Dawn Sturgess were taken ill.

Tests showed both had been exposed to novichok which had been in a perfume bottle Mr Rowley had found and given to Ms Sturgess. She did not recover from the contamination and died four days later.

In September the world’s chemical weapons watchdog, the Organisation for the Prohibition of Chemical Weapons (OPCW), said the toxic chemical that Ms Sturgess was exposed to was the same nerve agent as that which poisoned the Skripals.

Igor Korobov was born in 1956 in Vyazma, a town in Russia’s Smolensk Oblast region. After graduating from the Stavropol Higher Military Aviation School he served in the Russian Air Force before joining the GRU in 1985.

Rising through the ranks, Vladimir Putin appointed him head of the organisation following the death of Igor Sergun in January 2016.