A group of independent UN rights experts strongly criticized Tehran Friday, warning thousands could still be detained after a deadly crackdown on mass protests last month and voicing alarm at reports that inmates have been tortured. The UN expert on the rights situation in Iran, along with more than a dozen experts -- on issues ranging from torture to freedom of assembly -- said they were "shocked at reports of the ill-treatment of those detained during the protests". The UN rights office said earlier this month that at least 7,000 people had reportedly been arrested in Iran since the mass demonstrations erupted in November. In a statement Friday, the rights experts said they believed thousands were still being held and called for their release. "Reports suggest that detainees are being tortured or are suffering other forms of ill-treatment, sometimes to extract forced confessions," said the independent experts, who are appointed by the UN but who do not speak on behalf of the world body. "Some are also reportedly being denied medical treatment, including for injuries caused by the security forces use of excessive force," they said, adding that yet others were being held "incommunicado or subjected to enforced disappearances". The experts voiced deep concern at the lack of due process, warning that many of the detainees would likely be denied their right to a fair trial. The protests began on November 15 following a surprise hike in fuel prices. Iran has yet to give overall figures for the number of people killed or arrested when security forces moved in to quell the unrest that saw buildings torched and shops looted. Amnesty International said earlier this week that at least 304 people were killed during just three days of the crackdown. Iran has dismissed such figures as "utter lies", but the UN experts said Friday they had "credible sources" confirming that figure, adding that at least 12 of those killed were children. And they said that unconfirmed reports suggested the toll could be above 400. "The number of deaths appears to be particularly high in some provinces with large ethnic minority populations," Fridays statement said.Aiming to kill The experts pointed to reports and footage showing Iranian security forces "not only fired live ammunition at unarmed protesters, but also aimed at their heads and vital organs." "Targeting these parts of the body shows that the security forces were aiming to kill or at least cause serious injury," they said, adding that they were "extremely disturbed that the Iranian authorities would use such tactics against peaceful protesters." The experts also criticized Iran for continuing to suppress peoples right to free expression, even after easing an initial internet shutdown. "Most disturbingly, the families of individuals killed by security forces have allegedly been threatened not to speak out," they said. At the same time, Iranian journalists have been "ordered not to criticize the government response, while the relatives of journalists working for Farsi-language news outlets abroad are being pressured in an effort to silence their reporting," they said.