Russian President Vladimir Putin offered condolences to Korobov's family but did not immediately name his successor. "He dedicated his life to serving the Fatherland, defending national interests and strengthening security of our state," Putin said in a statement released by the Kremlin.
The United States and its allies have accused the GRU of hacking the 2016 U.S. presidential campaign, orchestrating the March nerve agent attack on a Russian ex-spy in Britain, and disrupting anti-doping efforts in world sports. Russian authorities have rejected the accusations, calling them part of a Western smear campaign.
This has been a tough year for the GRU, which has faced a series of exposures that revealed its inner workings. In September, British intelligence released surveillance images of GRU agents accused of the nerve agent attack on former GRU officer and British double agent Sergei Skripal and his daughter in the English city of Salisbury. The investigative group Bellingcat and the Russian site The Insider quickly exposed the agents' real names, and media outlets including The Associated Press were able to confirm their real identities.
Dutch authorities also have recently identified four alleged GRU agents who tried to hack the world's chemical weapons watchdog from a hotel parking lot. Putin visited the GRU headquarters earlier this month to congratulate the agency on its centenary, praising the agency for its professionalism.
Kremlin spokesman Dmitry Peskov said Thursday that the president had maintained a "regular dialogue" with Korobov as the chief of one of the nation's top intelligence agencies. He added that Korobov took part in a series of meetings on military issues chaired by Putin this week.