Blake was jailed in the 1960s for betraying the British foreign intelligence service but escaped and spent the rest of his life behind the Iron Curtain.
The former British double agent George Blake has died at the age of 98, Russian news agencies announced Saturday.
"Today, the legendary intelligence officer (...) George Blake, is no more. He sincerely loved our country, admired the achievements of our people during the Second World War," Sergei Ivanov, spokesman for the Russian foreign intelligence services (SVR), told the state agency TASS.
Born in Rotterdam on November 11, 1922, Blake was a former member of the Dutch resistance during the Second World War. He then worked for the British foreign intelligence service MI6 during the Cold War.
He offered his services to the Soviets in the 1950s after witnessing American bombings of civilian populations in Korea.
He provided the names of hundreds of agents to the KGB and revealed the existence of a secret tunnel in East Berlin used to spy on the Soviets.
Denounced by a Polish double agent, he was sentenced in 1961 to 42 years in prison in Great Britain. He managed to escape from prison five years later with the help of a rope ladder and his cellmates.
While on the run, George Blake managed to cross the Iron Curtain via the German Democratic Republic (GDR).
Celebrated as a hero in Moscow, he had received the rank of colonel by the Russian intelligence services. Despite the fall of the USSR to which he had dedicated his life, he never regretted his actions.
George Blake was the last surviving member of a famous generation of British double agents, the "moles" that the USSR had managed to recruit in the middle of the Cold War.