Iran's opposition leaders faced new threats Thursday with the state prosecutor warning they could be put on trial if they do not denounce this week's anti-government protests - the worst unrest since the immediate aftermath of the disputed June election. Police firing tear gas and wielding batons dispersed opposition supporters trying again Thursday to gather in two locations in central Teheran, said an opposition Web site called The Green Road. Police detained many of them, it said. The information could not be independently confirmed due to restrictions barring journalists from reporting on opposition activity in the streets. The confrontation between Iran's clerical rulers and their opponents has returned to the streets in recent weeks, after a harsh crackdown immediately following the election had all but put an end to demonstrations. Despite a continuing tough response from security forces, the opposition movement has regained some momentum. In demonstrations on Sunday, at least eight people were killed in clashes between security forces and opposition protesters on Ashoura, a sacred day for Shi'ite Muslims. It was the worst bloodshed since the height of the unrest in the summer. That was followed by two days of pro-government protests Wednesday and Thursday in which crowds chanted calls for the execution of the opposition leaders. A group also posted an online threat that suicide squads were ready to assassinate those leaders if the judiciary did not punish them within a week. Some government supporters at the two days of rallies wore white funeral shrouds to symbolize a willingness to die in defense of Iran's clerical rulers. Several hundred turned out for Thursday's demonstration in southern Teheran outside the offices of Supreme Leader Ayatollah Ali Khamenei, state radio reported. State prosecutor Gholam Hossein Mohseni Ejehei said the opposition leaders could be accused of supporting people who defy God by protesting against the government on Sunday. He said the leaders may face charges of "supporting apostates," or those who go against God. His comments were published in the state-owned Iran newspaper. The police posted on their Web site about 100 pictures of opposition protesters involved in Sunday's demonstrations, asking the public to help identify and report them on suspicion of "damaging public property and insulting sanctities." Late Wednesday, Iran's official news agency IRNA reported that opposition leader Mir Hossein Mousavi and another top figure, Mahdi Karroubi, had fled Teheran amid threats. But Karroubi's son, Taghi Karroubi, disputed that report and told The Associated Press that his father and Mousavi, were both at their homes in Teheran. "The people who must escape are the ones whose hands are tainted with the blood of Iranian people," Taghi Karroubi said. "Unfortunately, the government news agency is spreading false news like the government itself." One of those killed on Sunday was the nephew of Mousavi. The opposition says Ali Mousavi was shot and killed by security forces. But Iran's deputy police chief, Ahmad Reza Radan, said Wednesday that the way he was killed suggests he was assassinated while walking by unidentified assailants. Hundreds of opposition activists on Thursday gathered at his grave in Teheran's Behesht Zahra cemetery, said The Green Road Web site. Officials said more than 500 protesters have been arrested since Sunday's clashes and the number could be even higher. Many will likely be tried for apostasy - a crime punishable by death under Iranian law - as well as attempts to topple the government and fomenting the postelection turmoil. Iran has already sentenced five defendants to death in an ongoing mass trial of more than 100 opposition activists and figures. More than 80 were sentenced to prison from six months to 15 years. Ejehei said prosecution of the opposition leaders would not be forgotten. "The charge of supporting apostates and those who defied God will be added to their past charges," he said. Iran's deputy chief of judiciary, Ebrahim Raisi told the official IRNA news agency on Thursday that those detained over Sunday's unrest would be charged with violating public order and "Moharebe," which is Farsi for defying God.