The death of a young Iranian in custody for allegedly taking part in antiestablishment protests has heightened fears of brutal official reprisals against detained protesters and other perceived dissidents following the worst street demonstrations Iran has seen in nearly a decade.

Iranian activists probing the fates of detainees during protests and other unrest that erupted late last month reported on January 7 that 22-year-old Sina Ghanbari had died in prison of "unknown causes. "

The activists, who include lawyers and volunteers including individuals caught in past crackdowns like the one after a disputed presidential election in 2009, say their self-styled committee was informed of Ghanbari's death by other detainees following their release.

Well after the unconfirmed reports, the head of the prison authority in Tehran Province on January 8 said that Ghanbari had hanged himself in a prison lavatory.

"On the morning of Saturday, January 6, one of the prisoners, Sina Ghanbari, son of Ali Akbar, visited the lavatory of the quarantine section and hanged himself," Mostafa Mohebi told the semiofficial ISNA news agency.

Mohebi said a prosecutor had come to the prison and interviewed "prison guards and those informed" while also issuing "necessary orders."

The activists committee said via an announcement by activist Mehdi Mahmudian, a journalist and member of the reformist Participation Front who spent time in jail in 2009, that Ghanbari had been held in the quarantine section of Tehran's Evin prison, where detainees are frequently held before being taken to a general ward.

Fears Of Another Kahrizak

Mahmudian was reportedly crucial in informing the public about the abuses at Kahrizak, a detention facility where abuses were alleged in 2009.

Two Iranian lawmakers subsequently confirmed Ghanbari's death and suggested that the young man had committed suicide while in detention but did not offer details.

"This 22-year-old young man was arrested by the police. I was informed that he had committed suicide in jail," reformist lawmaker Tayebeh Siavashi was quoted as saying by the semiofficial ILNA news agency.

Another reformist lawmaker, Mahmud Sadeghi, made a similar statement to Etemadonline, saying that he had been informed through an unnamed "intelligence official" that Ghanbari had committed suicide in Evin.

Writing on Twitter, Sadeghi warned Iranian officials about a repeat of events following the 2009 protests, when reports emerged of detainees held at the Kahrizak detention center in Tehran being tortured and raped. At least three of those detainees died as the result of torture, rights groups reported.

"I'm warning the president along with judiciary and intelligence officials of a second Kahrizak," Sadeghi tweeted.

At least 22 other deaths have been reported in connection with the December-January protests but Ghanbari's is the first report of a death in custody.

"This news is like a knife stabbing the hearts of those whose young ones are in prison," said Mohammad Aghazadeh, whose son, Soheil Aghazadeh, is among some 80 students arrested recently.

"Even if [the news] is true, what did you do to them that they prefer to die than to tolerate your actions?" Aghazadeh asked in a separate tweet.

Wave Of 'Preventive' Arrests?

Some of the detained students were reportedly not among the protesters, but details are difficult to confirm due to official secrecy and restrictions on reporting in Iran.

An Iranian lawmaker said on January 5 that the authorities said that most of the students had been arrested as a "preventive measure."

Iranian authorities said that at least 450 people were arrested over a three-day span after the protests began in western Iran in late December. Subsequent reports suggest that well over 1,500 people have been arrested across the country, with some estimates much higher.

Dozens of detainees are said to have been released in recent days. However, hundreds remain in jail, and little has been said officially about their conditions.

Authorities have warned some of the families of those arrested not to speak to the media.

Kasra Nuri, a member of the Sufi Gonabadi order who previously spent several years in prison for his activism, is among those arrested. His mother, Shokoufeh Yadollahi, told RFE/RL's Radio Farda that Nuri had not participated in any of the recent antiestablishment protests.

"It's not clear why he was arrested. Kasra and three of his friends had gone to the Dey hospital [in Tehran] to visit a friend when security forces arrested them while using electric shockers and firing shots into the air," Yadollahi said in a telephone interview.

She added that her son was being held in Section 209 of Evin prison. Yadollahi and family members of him and of other detainees have gathered in front on the prison to appeal for their release.

Amnesty International demanded on January 4 that Iranian authorities "protect hundreds of detainees from torture and other ill-treatment."

"Given the alarming scale of the current wave of arrests, it is highly likely that many of those held are peaceful protesters who have been detained arbitrarily and now find themselves in prisons where conditions are dire and torture is a common tool to extract confessions and punish dissidents," Amnesty International's research and advocacy director for the Middle East and North Africa, Philip Luther, said.