In the Greek civil war following Greece's liberation in 1944, Kyrkos was arrested for his membership in the Communist Party and was sentenced to death.

Only international pressure helped him and a number of his comrades survive and eventually become free in 1953.

[1] On 21 April 1967, during the coup d'état that installed the military junta, he was arrested and remained imprisoned for five years.

[1] Along with Charilaos Florakis, leader of the Communist Party of Greece, he founded the Coalition of the Left and Progress (Synaspismós), of which was secretary until March 1991.

[1] His son Miltos Kyrkos in 2014 was elected Member of the European Parliament for the party To Potami.