MOSCOW (AFP) - Russia has replaced the head of its GRU military intelligence organisation, who presided over major reforms of the secretive body, a defence ministry spokesman said on Monday. "Major General Igor Sergun has been appointed the head of the GRU through a Kremlin decree," a defence ministry spokesman told AFP.  Sergun replaces Alexander Shlyakhturov, who had spearheaded a shake-up of the service since his appointment in 2009. The defence ministry spokesman did not provide further details. 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.