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

Igor Korobov, who led Russia's Main Directorate of the General Staff of the Armed Forces, often referred to as the GRU, died on Wednesday "after a long and grave illness," the TASS news agency reported.

"Defence Minister General of the Army Sergei Shoigu on behalf Russian Defence Ministry expresses condolences over death of Head of the Main Directorate of the General Staff Colonel General Igor Korobov," Russia's Defense Ministry said in a statement.

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The ministry added in a statement reported by The Guardian: “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."

Korobov joined the Russian military in 1973 and had worked in military intelligence since 1985 in various positions, according to the Defense Ministry.

He was appointed in early 2016 by Russian President Vladimir Putin to take over the GRU following the death of his predecessor at the helm of military intelligence, Igor Sergun, who died at the age of 58.

Korobov was also among the Russian intelligence officials sanctioned by the Obama administration in December 2016 when the U.S. expelled 35 Russian operatives and announced other retaliatory measures in response to a hacking campaign from Russia during the U.S. presidential election that year.

Britain has said it believes the GRU orchestrated the nerve-agent attack against former Russian spy Sergei Skripal and his daughter, Yulia, in Salisbury, England, earlier this year, which Russia has denied.

Vice Admiral Igor Kostyukov, the first deputy head of the GRU, has been tapped as the intelligence agency's acting head, TASS reported, citing a Defense Ministry source.