Evren had received treatment at the GATA military hospital since 2012 but his condition turned critical on Saturday when he was taken out of an intensive care unit and attached to a respirator.
His lawyers and family were summoned to the hospital, Anatolia said.
The former president was sentenced to life in prison last June along with former air force commander Tahsin Sahinkaya, 90, for their roles in the putsch 35 years ago.
The two were the only surviving members of the junta at the time of the trial.
As head of the armed forces, Evren seized power in a pre-dawn assault on September 12, 1980, and went on to rule for the next nine years. (AFP)