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Igor Korobov, head of Russian military intelligence, dies age 62 -- state media

Moscow(CNN) The head of Russian military intelligence has died at the age of 62, Russian state news agencies reported Thursday.

Igor Korobov, the head of the Main Directorate of the General Staff, died after what the Russian military described as a "serious and prolonged illness," state news agency RIA-Novosti reported.

Korobov was appointed head of the GRU in February 2016. His predecessor in the role, Igor Sergun, had died the previous month at the age of 58, having headed the agency since 2011, according to Russian state news agency TASS.

The Main Directorate -- traditionally referred to as the GRU -- is accused by the West of being behind a string of brazen attacks against international targets.

Britain believes the GRU orchestrated the nerve agent attack in Salisbury, England, earlier this year against former Russian double agent Sergei Skripal and his daughter, Yulia.

The investigative website Bellingcat, which claimed to have uncovered the real identity of the two Russian men suspected of involvement in the Salisbury poisonings, said they were GRU officers, contradicting official Russian claims that the two were ordinary citizens.

The Dutch government also accused the GRU last month of targeting the world's chemical weapons watchdog, the Organisation for the Prohibition of Chemical Weapons (OPCW), through a foiled cyber operation.

Dutch and UK officials gave unprecedented details of what some international media outlets labeled a botched Russian mission.

On the same day, Britain, backed by close intelligence allies Australia and New Zealand, pointed the finger at the GRU for carrying out a worldwide campaign of "malicious" cyberattacks, including the hacking of the US Democratic National Committee in 2016.

Russia dismissed the allegations of GRU involvement.

Kremlin spokesman Dmitry Peskov said Thursday that Russian President Vladimir Putin had been in "constant dialogue" with Korobov.

Speaking on a conference call with reporters, Peskov said Korobov had participated in a recent meeting with Putin in the southern Russian resort city of Sochi, but said there was no one-on-one meeting with the intelligence chief.

"Of course they had a constant dialogue as a commander-in-chief and a head of one of the leading special services," Peskov said. He added that Putin had already expressed condolences to Korobov's family, his relatives and colleagues.

Peskov referred questions about the circumstances of Korobov's death to the Russian Ministry of Defense.

Korobov, along with other Russian intelligence chiefs, visited Washington in February 2018, according to TASS, despite being on a US sanctions list for being "responsible for or complicit in malicious cyber-enabled activities." However, he did not meet with US Secretary of State Mike Pompeo while in the US capital.

Korobov had been added to the US sanctions list in December 2016, in the closing days of the Obama administration.

According to a brief profile published by TASS, Korobov joined the military in 1973 and began working in military intelligence in 1985. He occupied a number of different positions in the agency, and spoke several foreign languages, TASS reported.

The Russian Defense Ministry gave no information on how or where Sergun, his predecessor, died, according to a 2016 TASS report. He had been placed on an EU sanctions list in 2014 following Russia's illegal annexation of Crimea for his alleged role in directing GRU activities there.

Russian male life expectancy was 67 as of 2016, according to the World Bank.

Update: Korobov's age has been corrected based on new information from Russian state media. He was 62.

CNN's Nathan Hodge reported from Moscow and Laura Smith-Spark from London. CNN's Sebastian Shukla and Darya Tarasova contributed to this report.