MOSCOW — The head of the Russian military's main spy service, Colonel General Igor Sergun, died Jan. 3 at age 58.
A ministry statement said he died suddenly but gave no further information on the death.
The military intelligence service, widely known by the acronym GRU, is believed to be Russia's largest foreign intelligence operation.
Mr. Sergun was appointed to head the GRU in 2011.
Previously, the career officer had been Russia's military attache in Tirana, Albania.
He leaves his wife and two daughters.