The headquarters of the Venezuelan intelligence service is a vast pyramid-shaped edifice known as the Helicoide, a former shopping mall which now functions as an interrogation pen for political prisoners and protesters.

The 30-year-old economics student had heard enough about the infamous building to be terrified as he was led into a dank cell in early April — his eyes blindfolded, his wrists bound by his shoelaces.

“You’re going to die here,” a guard informed him, he later recalled.

The student had been detained after throwing rocks at an anti-government protest. During the 12 hours he spent inside the Helicoide, he said, the guards pummeled his torso, gave him electric shocks and ignited a type of powder in his cell that had the effect of tear gas, causing him to press his face into the concrete floor to escape the fumes.

Over the past 10 weeks of protests in Venezuela, security forces have detained more than 3,200 people, with over a third of them remaining in custody, according to Foro Penal, a legal aid group. Allegations of mistreatment during the arrests and detention have ballooned, according to human rights groups. They come as authorities have also begun to send demonstrators to military courts, where they can face charges of treason and rebellion that carry lengthy sentences.

(Joshua Partlow,Jason Aldag/The Washington Post)

The government’s fierce crackdown on the demonstrations, along with its efforts to disband the legislature and change the constitution, have brought international condemnation and fueled debate over whether Venezuela is sliding toward dictatorship.

“We have to call things by their name, and what we have here is a country that, in fact, has ceased to be a functional democracy, and this is a tremendously dangerous thing for the region,” Mexico’s foreign minister, Luis Videgaray, said in May.

Nearly as many people have been detained in the past two months during anti-government demonstrations as in all of 2014, a year of intense protest in Venezuela, said Nizar El Fakih, director of the human rights organization Proiuris.

Some demonstrators say they are picked up by security forces who manhandle them and hold them in overcrowded detention centers. The worst treatment appears to be meted out by the intelligence service and the armed forces, whose prisoners have endured regular beatings and sometimes other forms of physical and sexual abuse, according to interviews with former detainees, defense attorneys and human rights advocates. While Venezuelan security forces have been accused of using excessive force in the past, the upsurge in such allegations has alarmed human rights activists.

“We’ve noted a great increase in the number of torture and cruel, inhumane-treatment cases,” El Fakih said, noting there are no definitive numbers on the phenomenon. “I can say that the increase has been exponential.”

The office of President Nicolás Maduro — as well as the National Guard, the National Police and the Ministry of the Interior — did not respond to repeated requests for comment about the allegations. But the government has publicly defended its actions against the demonstrators and reiterated its commitment to human rights.

“The National Guard and the National Police have made a heroic effort and should keep doing it, with no firearms, no pellets, only water and tear gas,” Maduro said on television this past week.

Interrogated while detained

The current unrest began with peaceful marches against what protesters call an increasingly authoritarian government and an economic crisis. But the demonstrations have devolved into chaotic street battles between protesters hurling rocks and molotov cocktails at National Guard and police, who fire water cannons, tear gas and rubber bullets.

At least 70 people have died, and more than 1,300 have been injured in the demonstrations.

The economics student, who spoke on the condition of anonymity out of fear of retribution by the government, said that during his detention in the Helicoide, intelligence agents interrogated him about whether he worked with opposition political parties and scoured his social-media accounts.

At one point, after he was zapped with a stun gun three times, he begged to borrow a cell phone to call his mother, the student recounted.

“Do you think you’re in Disneyland?” he recalled a guard taunting him.

The student was eventually taken to a police station in downtown Caracas, where he spent 29 days handcuffed to another detainee before being released on a charge of public disorder, he said. The only severe physical abuse he suffered, he said, occurred in the Helicoide, a facility that repeatedly comes up in protesters’ allegations of mistreatment.

The student’s account, and those of the other ex-detainees interviewed for this story, could not be independently confirmed. But they have similar characteristics to other testimonies gathered by human rights groups.

Maduro’s administration says the street demonstrations are aimed at overthrowing the government. Authorities have begun to send protesters to military tribunals, with more than 300 facing charges such as rebellion against the state, which carry sentences of decades in prison. This shift comes as the attorney general, Luisa Ortega Díaz, has emerged as a critic of the Maduro administration.

“This is a way to bypass the attorney general when she’s started to identify that security forces are committing abuses and are using excessive force against detainees,” said Tamara Taraciuk Broner, Americas senior researcher at Human Rights Watch.

The government releases little information about those who get arrested, and families are often in the dark about their situation.

Many of those detained say they were not involved in any violence. In early May, two National Guardsmen converged on Ana Rosa Cisneros, a 41-year-old single mother, as she was leaving a pharmacy near one of the protests, she said.

“I was caught in the middle of tear gas and rubber bullets, and I wasn’t even protesting,” she said. “They hit me, pulled my hair, dragged me to a car and insulted me.”

Cisneros, who works as a cleaner at an Italian restaurant in southeastern Caracas, spent 16 days in a National Guard detention facility in a small room with seven men, she said. She was charged with illegal association and must report to court monthly.

Argenis Ugueto, 27, and five of his friends said they were detained by the National Guard on April 19, as they walked to an afternoon protest, wearing hats and shirts in the colors of the Venezuelan flag. The National Guard — who are part of the armed forces — accused them of being guarimberos, the name for violent, front-line protesters, he said. At the National Guard headquarters in western Caracas, Ugueto said, the guards planted molotov cocktails and helmets in their belongings.

“They wanted us to be scared but at the beginning we weren’t because, you know, we thought we were innocent,” said Ugueto, a former communications student from the port town of Catia La Mar. “That’s when they started hitting us.”

Ugueto said he was held at the base for 30 days, with the guards punching him repeatedly in the face and torso. He was charged with inciting violence and released with a requirement to check in with authorities.

“They made us sign a form where it says they didn’t treat us badly, and of course we all signed,” he said, due to “the fear of not knowing what would happen.”

Human Rights Watch documented a case in May in the city of Valencia in which 40 people were arrested near a food company that had been looted the day before, and brought before a military judge on charges of rebellion. During the hearing, some showed bruises and said they had been beaten by members of the National Guard with aluminum rods and baseball bats.

“At least 15 said they were forced to eat raw pasta with human excrement — the officers allegedly put tear gas powder in their noses so they would be forced to open their mouths to eat,” the Human Rights Watch report read.

Detainees have reported that the prisons are dismal, with detainees forced to sleep on dirty concrete floors and sometimes defecate in plastic bags. One young woman arrested on her way to a protest, Yusneimi Lopez, was so upset at the prison conditions that she tried to hurl herself out of a window of a courthouse during her preliminary hearing, according to Gonzalo Himiob, who attended the hearing and works with Foro Penal.

A woman detained with Lopez, Yajaira Braque, said that the woman had told her earlier that day that her time in prison had been so miserable that if she was convicted and sent back, “she would commit suicide.”

Mariana Zuñiga contributed to this report.