BEIRUT (AP) -- About 30 security agents showed up just after midnight, breaking down the door to an apartment in the town of Daraya near the Syrian capital of Damascus. They grabbed a 24-year-old university student and drove off.
That was a year ago. The young man, who had been providing aid to Syrians displaced by the country's civil war, was never heard from again. His family was told by former prisoners that he ended up in one of the torture dungeons of President Bashar Assad's regime. They don't know if he's dead or alive.
More than two years into the conflict, such accounts have become chillingly familiar to Syrians. Intelligence agents have been seizing people from homes, offices and checkpoints, and human rights activists say the targets often are peaceful regime opponents, including defense lawyers, doctors and aid workers.
Syrian human rights monitors say the number of those disappeared without a trace is now in the thousands. By comparison, the official figure of those who disappeared in Argentina's "dirty war" of the 1970s and 1980s is about 13,000, though rights activists say the actual figure is more than twice that.
In such "enforced disappearances," governments refuse to acknowledge detentions or provide information about those taken. The point traditionally is to get rid of opponents and scare the rest of the population into submission -- a rationale laid out in Adolf Hitler's "Nacht und Nebel (Night and Fog)" decree of 1941.
In Syria, the goal is to "terrorize the society and dry up the revolution," said Anwar al-Bounni, a veteran defense lawyer and human rights campaigner in Damascus. "The regime focuses on arresting peaceful activists to turn it purely into an armed conflict."
However, numbers remain sketchy.
Four Syrian human rights monitors offered separate estimates ranging from about 10,000 to as many as 120,000 disappeared. The two lower estimates are based on information from families and released prisoners, while the higher figures are based on extrapolation from partial data.
Two international groups, Amnesty International and Human Rights Watch, said they believe a majority of detainees in Syria are held under conditions amounting to enforced disappearance. Amnesty said it estimates that tens of thousands of Syrians are in detention but does not have exact figures.
The wide range of numbers also reflects the difficulty of collecting information at a time of chaos, on a practice the regime doesn't acknowledge.
A U.N. panel said in a 2013 report that when it asked about allegations of thousands of enforced disappearances in Syria, the Assad government responded that "there were no such cases in Syria" and that all arrests were being carried out legally.
The accounts by rights groups and those given to The Associated Press by relatives and friends of five of the missing tell a different story -- of arbitrary arrests, of detainees languishing incommunicado in underground cells that are so crowded they have to sleep standing up and of torture to the point of death.
A relative of the university student said that when security forces barged into her family's apartment in Daraya on May 19, 2012, they initially asked for a man who didn't live there.
They searched the apartment, and left, apparently to consult with an informer, said the woman who spoke on condition of anonymity for fear of further regime reprisals. A different group returned a few minutes later and asked for the family member who was studying for a master's degree. The young man stepped forward and was taken, she said.
Three months later, a released prisoner told her that her relative was being tortured at a large detention center run by air force intelligence at Mezzeh Airport near Damascus.
Six months after the arrest, another released detainee told her he had fed her relative because he had lost use of his hands. A third former prisoner told her that her relative was taken to a prison hospital in very bad condition about five months ago, never returned and most likely had died.
Uncertainty weighs heavily on the families. "It is psychological torture for everyone in the family," she said in a phone interview from exile. "No news. One says he is dead, the other says he is not."
In the town of Banias on Syria's Mediterranean coast, the Sahyouni family has been living in limbo for two years.
In May 2011, three months after the start of what was then still a largely peaceful uprising, brothers Ghassan, Bashar and Mohammed Sahyouni reported to the local office of the military intelligence. They had joined the protests, but hoped to take advantage of an amnesty promised by Assad at the time.