The head of Russia's secretive GRU military intelligence service, Gen Igor Sergun, has died suddenly aged 58, the BBC reported. 



Expressing condolences, President Vladimir Putin called him "an experienced and competent commander, a man of great courage, a true patriot". 



The circumstances of his death are not clear. He became GRU chief in 2011. 



In 2014 he was placed on EU and US sanctions lists targeting top Russian officials after Russia's annexation of Crimea, in southern Ukraine. 



The EU list said Gen Sergun was "responsible for the activity of GRU officers in eastern Ukraine". 



Gen Sergun is not thought to have had direct combat experience when he took charge of the GRU. 



After graduating from military academies, he joined the service in 1984, and had various posts before working as military attache in Albania in 1998

Source: NNA