The government has made it a practice to publicize confessions from political prisoners held without charge or legal representation, often subjected to pressure tactics like sleep deprivation, solitary confinement and torture, according to human rights groups and former political prisoners. Human rights groups estimate that hundreds of people have been detained.

In 2001, Ali Afshari was arrested for his work as a student leader. He said he was held in solitary confinement for 335 days and resisted confessing for the first two months. But after two mock executions and a five-day stretch where his interrogators would not let him sleep, he said he eventually caved in.

“They tortured me, some beatings, sleep deprivation, insults, psychological torture, standing me for several hours in front of a wall, keeping me in solitary confinement for one year,” Mr. Afshari said in an interview from his home in Washington. “They eventually broke my resistance.”

Three years later, Mr. Memarian, the journalist and blogger, was arrested in another security sweep. He said that his interrogator at first sought to humiliate him by forcing him to discuss details of his sex life, and that when he hesitated, the interrogator would grab his hair and smash his head against the wall. He said the interrogator asked him about prominent politicians he had interviewed, asked if they ever had affairs, and asked if he had ever slept with their wives.

“I was crying, I begged him, please do not ask me this,” said Mr. Memarian, who is in exile now in the United States. “They said if you don’t talk now you will talk in a month, in two months, in a year. If you don’t talk now, you will talk. You will just stay here.”

The pressure was agonizing, he said, as he was forced to live in a small cell for 35 days with a light burning all the time and only three trips to the bathroom allowed every 24 hours. He was forced to shower in front of a camera, he said. At one point the interrogators threatened to break his fingers.