Five police trucks loaded with masked and armed men dressed in civilian garb surrounded them. Uniformed officers began to search the students' backpacks. One pulled out a blue-and-white Nicaraguan flag.
"These are the terrorists who killed our fellow police," the officer shouted, using President Daniel Ortega's term for those who have protested against his government since mid-April.
The young couple and their friends joined the ranks of more than 2,000 people arrested in Nicaragua in nearly four months of unrest and official crackdown. At least 400 people are believed to still be held in jails, prisons and police stations, and some consider them political prisoners, the non-governmental Nicaraguan Human Rights Center says.
The others were held for days or weeks incommunicado, brutally interrogated to give up names and threatened with terrorism charges before being released without explanation as Ortega's government seeks to extinguish the resistance.
"They crushed my fingers, and hit me in the ribs and the stomach," the pregnant student said. "When I was on the ground, they kicked me."
The Associated Press separately interviewed four of those arrested and released, all of whom are in hiding. They agreed to speak only on condition of anonymity out of fear of retaliation.
"Right now, without exaggerating, Nicaragua is a prison," said Vilma Nunez, the rights center's president and a former supreme court vice president under Ortega's first Sandinista government in 1979. She called Ortega's systematic search for those involved in the protests a "human hunt."
Last week the Inter-American Commission on Human Rights said its monitoring team in Nicaragua found that detainees were abused, not informed of their rights or any charges, and taken into custody without warrants. Their families were not told where they were held, it added.
National police did not respond to a request for comment.
Ortega for weeks denied that paramilitary squads and Sandinista youth groups that have clashed with or attacked protesters were working with the police. But when asked in a recent TV interview how demonstrators picked up by masked paramilitaries ended up in jails, he said: "We have volunteer police who cooperate with the police."
He has accused protesters and opponents of trying to stage a coup.
The unrest began as protests to social security cuts. After a deadly crackdown, students became the vanguard of a broader push demanding Ortega step down.
The young woman from the National Autonomous University of Nicaragua was among nearly 200 students who dug in at the Managua campus, only to be driven out in mid-July by paramilitaries under heavy gunfire that killed two people.
A short time later, she and others were taken to a police processing center and lined up with their hands behind their necks.
"I told (one) I was pregnant," she said. "'Ah,' he says, 'great. We've got a pregnant one.'"
"One of the paramilitaries came and punched me in the stomach," she said. "'Now we're going to get it out of you,' he said. 'And you're going to eat it alive.'"
The men and women were separated and interrogated individually. The men were stripped naked.
A 20-year-old business administration student from the national university said he was punched in the stomach and kicked in the testicles. A police officer ripped out his eyebrow piercing, and a cigarette was put out on a tattoo on his shoulder.
"They said they were going to rape us. They said they were going to rape the girls," he said.
Police and masked civilians asked the same questions in the interrogations: Who were the student leaders? What political party was financing their movement? How much were they being paid? What weapons did they have?
A 24-year-old student at the national university said a female police officer threatened her with a knife and slapped her.
A 23-year-old woman who recently graduated from another university said she was hit with a rifle butt.
Her boyfriend, whom they suspected of being a leader, suffered worse. "They put a cigarette on his testicle," she said.
The pregnant student was taken to a room and made to stand with her hands spread out on a table. The interrogators began hitting her in the stomach once more, she said, and a female officer cut off half her toenail.
When she again told them she was pregnant, they told her: "The pain is what we feel fighting for the country. You all just want to see the country destroyed. You want to see our commander (Ortega) go."
Midway through her five-day incarceration she started to bleed. She was interrogated and beaten again.
When the students were finally released they were warned to stay out of sight or they would be charged with terrorism.
The next day she went to a hospital, where a doctor told her there was nothing they could do.
"They told me to prepare myself for the news," she said. "I lost my baby."
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