BEIRUT — The young man waved a pistol at them.
"I am your judge," he said as he aimed his weapon at the faces of the prisoners, who were protesting their innocence and loudly complaining about their treatment.
"If you shout again, I can shoot," he continued. "If you are brave enough to go out on the streets to protest, you should have the guts to be brave here too."
The book publisher, who had been arrested at his office, said he was speechless.
"What kind of judge," he recalled wondering to himself, "wields a gun?"
Iran's supreme leader, Ayatollah Ali Khamenei, has called on both sides in the dispute over the June 12 presidential election to cool the tempers of their young supporters. But whereas supporters of defeated candidate Mir-Hossein Mousavi can arm themselves with stones or e-mails, backers of the hard-line incumbent, Mahmoud Ahmadinejad, appear to have the hard instruments of the state at their disposal.
The middle-aged book publisher, who was detained in a crackdown against dissidents and alleged rioters, asked that his name be withheld for fear of retribution. Though he supported Mousavi, he denies taking part in any protests.
His tale of a week of detention, recounted in an interview Sunday, jibes with accounts of other detainees, many of whom have been released.
Some, including political analyst Bijan Khajepour, who was arrested on his return after a visit to Britain, and reformist Saeed Hajjarian, who has used a wheelchair since a 2000 assassination attempt, remain in jail.
"It's never a good time for human rights in Iran, but the scale of what's going on in response to the protests over the results of the elections is beyond anything we've seen in recent times," said Tom Porteous, a London-based official for Human Rights Watch, which has collected the names of more than 300 people who have been arrested. "We're very concerned about the potential for the mistreatment of those who've been arrested."
It was 7:30 p.m. on June 20, the day riots engulfed Tehran, when police pounded on the door of the publishing house, across the street from Tehran University.
The publisher, who agreed to be identified only by the initial M, and his colleagues were tabulating accounts and updating their ledger.
"Open up!" the officers demanded. "Security police!"
M opened the door to three security officers, who were wearing helmets and wielding truncheons. The police began swinging the truncheons at the legs and calves of M and his colleagues.
"You were filming the scenes in the streets . . . from your balcony," one officer charged.
M offered to let them examine their cellphones. "Look at them," he recalled pleading. "We have not done anything wrong." Still, they were detained.
"Our commander has video of all who have taken photos and photos of protesters," one officer told them. "If your faces aren't there, we will let you go immediately."
Instead, they were locked up in an underground cell near Tehran's Enghelab Square and then taken to another police station in south Tehran. There, the publisher said, he and about 200 other people were crammed into a courtyard and forced to stand in the hot sun without food or a place to rest. Nearly 36 hours passed.
That's when the gun-waving young man arrived.
After threatening the prisoners, he handed out forms that asked a single question: "Do you accept the charge of being involved in riots against national security and law and order of the country?"
Everyone reluctantly acknowledged the charges, M said. After collecting signatures, the man disappeared.
Other prisoners said that during these initial hours, they were pummeled by Basiji militiamen who told them they had been inspired to crack down by Khamenei's tears during a Friday sermon, which many interpreted as a green light.
" 'You have caused my beloved leader to burst into tears,' " another prisoner said he was told. " 'Now you deserve to be beaten.' "
Hours later, prisoners were packed into two buses, so crowded that they could barely move.
They were headed to the notorious Evin Prison, but M said he was relieved to get there. He knew that's where his family would look for him first. But he was horrified to learn that more than 500 prisoners would be crammed into a cell of about 500 square feet.
Older than most of the prisoners, M was designated the cellblock leader, in charge of scheduling four-hour sleeping shifts for the inmates, who had to stand during the rest of the time, share a single toilet or make quick calls to their family on a single phone.
At mealtime, they ate watery bean or noodle soup. To kill time, they debated politics and the nation's future.
Prisoners were frequently singled out and pulled away for interrogation. They came back hours later with bruises or with blood in their urine, he said. Some would be pulled out at 8 a.m. and returned 14 hours later, limping and exhausted.