Iran's Supreme Leader Ayatollah Ali Khamenei warned the country's reformist opposition on Friday it would face a "harsh response" for confronting the Islamic establishment. The remarks were a clear threat to the Iranian opposition and reformists who have challenged Khamenei's authority in the aftermath of the disputed June presidential election. Khamenei, who has final say on all state matters, has supported President Mahmoud Ahmadinejad's re-election and has dismissed opposition claims that Ahmadinejad's victory in the vote was fraudulent. The pro-reform opposition says Ahmadinejad stole the election through massive vote fraud and that its leader Mir Hossein Mousavi was the true winner. Khamenei, who led Friday prayers in Teheran, said authorities would strongly punish those who "take up the sword" to "confront the principles of the Islamic system." But, he said, peaceful differences and criticism by officials would be tolerated. The sermon was broadcast on state television. "Confronting the system and drawing a sword against the system will bring a harsh response," Khamenei said. A heavy security crackdown crushed the opposition protests following the proclamation of Ahmadinejad's victory in the June 12 vote. Khamenei and other hard-liners have attempted to paint the post-election turmoil as a plot by Iran's foreign enemies to overthrow the country's Islamic system through a "velvet revolution." The government is holding a mass trial of more than 100 detained political activists and protesters who it claims provoked the mass demonstrations. The opposition counters that the ruling system - beyond just Ahmadinejad's elected government - is losing its religious and political legitimacy because of the harshness of the postelection crackdown. Mousavi and another defeated presidential candidate, Mahdi Karroubi, have dismissed Ahmadinejad's government as "illegitimate" and vowed to confront the establishment by exposing reports that detained male and female protesters were brutally abused, even raped by their jailers and several tortured to death - allegations that have deeply embarrassed the government and the clerical leadership. The opposition says at least 72 protesters were killed while Iranian officials have said 36 people died in the post-election turmoil - Iran's worst unrest since the 1979 Islamic Revolution. About 200 protesters and opposition figures remain in detention.