Russia has appointed new head of military intelligence (GRU), a day after ex-chief resigned from his post to join a company that develops nuclear missile. "Major General Igor Sergun has been appointed the head of the GRU through a Kremlin decree," a defense ministry spokesman said on Monday. Sergun replaces Colonel General Alexander Shlyakhturov, who spearheaded a shake-up of the service since his appointment three years ago. The 64-year-old general is set to head the board of directors of the Moscow Institute of Heat Engineering, the developer of the Bulava ballistic missile and other strategic missile systems in the near future. Russian Defense Minister Anatoly Serdyukov highly trusts Shlyakhturov, according to informed sources in the Russian armed forces. Russian President Dmitry Medvedev appointed Shlyakhturov as the head of the Russian military intelligence service in 2009. The state RIA Novosti news agency said, citing a ministry spokesman that Shlyakhturov had reached retirement age. No other reason was given for the move. The GRU (Main Intelligence Directorate) traces its history back to 1918 and unlike other Russian secret services did not change its name after the collapse of the Soviet Union. It reputedly runs vastly more agents abroad than the KGB's successor, the Foreign Intelligence Service (SVR), and is also active in space through a network of military intelligence satellites.