Updated

Iranian authorities are using beatings, sleep deprivation and long interrogations to force confessions from those detained in the country's postelection turmoil, an international human rights group said Wednesday.

Human Rights Watch said in a report that the confessions appear meant to support claims by Iranian government officials that foreign powers were driving the unrest and that the protests were aimed at overthrowing the government, rather than holding a new election.

Claims of fraud in President Mahmoud Ahmadinejad's June 12 re-election set off days of street protests that were subsequently quelled by a harsh crackdown. Iran's reformist opposition has called for the result to be annulled and for a new election to be held.

"The Iranian government is desperate to justify its vicious attacks on peaceful protesters," said Sarah Leah Whitson, the Middle East and North Africa director for Human Rights Watch. "What better excuse does it need than confessions of foreign plots beaten out of detainees?"

The group said detainees whose accounts it collected included a 17-year-old boy detained on June 27 and coerced into signing a blank confession to be filled in later by authorities.

He told the group he was forced to stand in a parking garage for 48 hours with other detainees that had been rounded up. With their hands tied behind their backs and their eyes blindfolded, they were beaten repeatedly with batons.

That group of detainees — ranging in age from about 15 to 70 — were denied water while being held for five days and were given bread to eat on just one occasion, Human Rights Watch quoted him as saying.

On the last day, they were made to sign a piece of paper that was blank except for the words: "I agree with all of the above statements," according to the account.

The rights group's report also included what it said was an account from a witness who visited the Revolutionary Court on July 1 and saw a number of detainees being released who had bruises on their faces and hands.

Police say more than 1,000 people were arrested in the violence and in sweeps that followed and that most have been released. Still, dozens of protesters, pro-reform politicians and journalists are still being held, and arrests have continued.

Iran's state media have broadcast what they said were confessions from some detainees.

The country's hard-line leaders have been trying to erase doubts about the legitimacy of Ahmadinejad's government by portraying the unrest as sparked by foreign meddling, singling out Britain.

Human Rights Watch said one of the detainees forced to appear on Iranian television was Newsweek correspondent Maziar Bahari, who has Iranian and Canadian citizenship.

Bahari has been charged with "agitating against the ruling system and acting against national security," according to lawyer Saleh Nikbakht, who is representing a number of prominent reformist leaders being held.

Human Rights Watch said it collected the names of 450 people whom security forces have arrested since the election, including more than 100 political figures, journalists, human rights defenders, academics and lawyers.

Verifying information on detainees has been difficult, as Iran has restricted media activity during the unrest.

"Most of the best-known detainees have now been held incommunicado for up to three weeks without access to lawyers or family members, raising serious concerns about the probability of mistreatment and pressure to make false confessions," the Human Rights Watch report said.