Nearly 90 professors at Teheran University have told Iran's supreme leader that ongoing violence against protesters shows the weakness of the country's leadership, a pro-reform Web site reported Monday, reflecting a growing willingness to risk careers and studies to challenge the ruling clerics. The current rumblings from universities highlight the evolution of the opposition movement. What began as raw and angry voter backlash after last June's disputed presidential election has moved to a possibly deeper and more ingrained fight against Iran's Islamic leaders. The letter signed by the 88 instructors was issued as university students around Iran staged acts of defiance - including hunger strikes and exam boycotts - to protest reported arrests and intimidation by hard-line forces, according to witnesses and reformist Web sites. The government, meanwhile, stepped up its accusations that the West is fomenting Iran's postelection turmoil, saying that foreign nationals were among those arrested in the most recent clashes. Officials didn't provide the nationalities of those arrested, but accused the foreigners of leading a propaganda war and warned they face possible death sentences for seeking to topple the system. Authorities also have tightened pressures on universities. Opposition groups also claim faculty members and students who publicly back the demonstrations have been fired or blocked from coveted postgraduate slots in state-run schools. But the pressures haven't appeared to undercut the widening role of universities in the showdowns. The symbolism of campus resistance resonates strongly in Iran. College students were one of the pillars of the Islamic Revolution in 1979. In the late 1990s, students spearheaded the early cries for greater social and political freedoms. The graying theocracy faces a critical generation gap and cannot afford to lose legitimacy among large portions of the youth in a country with nearly half its population under 25 years old, analysts say. "The universities are the little engines that make the big engine work," said Mehrzad Boroujerdi, an Iranian affairs expert at Syracuse University. "The students are the brains and the body of the opposition movement." The letter by the Teheran University professors - posted on the Greenroad Web site - called the attacks on opposition protesters a sign of weakness in the ruling system. It also urged Supreme Leader Ayatollah Ali Khamenei to order arrests over the hard-line crackdown, which intensified after protesters began chanting slogans against the supreme leader. There was no immediate reaction from Iran's leaders on the letter. But authorities have stepped up arrests after the latest wave of street protests by opposition groups in late December and have vowed an even more punishing response to any further protest rallies - which could next come in early February to coincide with the anniversaries of various events from the Islamic Revolution. At least eight people died in clashes between security forces and opposition supporters across Iran late last month, including a nephew of opposition leader Mir Hossein Mousavi. It was the worst bloodshed since the height of the unrest immediately after the June re-election of President Mahmoud Ahmadinejad. "Nighttime attacks on defenseless student dormitories and daytime assaults on students at university campuses, venues of education and learning, is not a sign of strength. ... Nor is beating up students and their mass imprisonment," the letter read. The letter referred to attacks by pro-government paramilitary Basij forces on pro-opposition students inside Teheran University campus last month. "Unfortunately, all these (attacks) were carried out under the pretext of protecting Islam" and the position of the supreme leader, the letter said. Teheran University is the country's largest, with 1,480 professors and teachers, according to its Web site. But smaller campuses also have become settings for stands by the opposition, according to reformist Web sites and witnesses. The witnesses spoke on condition of anonymity because of fear of arrest. At Razi University in the western city of Kermanshah, students posted a statement this week declaring they would not attend exams to protest arrests of classmates. In the eastern city of Mashhad, some students at Ferdowsi University began a hunger strike Sunday to demand the removal of security forces and hard-line vigilantes around the campus. "The reform movement is strong and increasingly assertive," said Nicholas Burns, a professor at Harvard's Kennedy School of Government and a former senior official at the State Department. "It now has a broader base within Iran that is no longer a struggle specifically over the stolen election." The government has accused the West of orchestrating Iran's worst internal unrest since the Islamic Revolution. Intelligence minister Heidar Moslehi said Monday some of those arrested in protests Dec. 27, when Shi'ite Muslims in Iran marked the sacred day of Ashoura, were foreign citizens. "Some of the detainees ... were foreign nationals who were leading a propaganda and a psychological war," said Moslehi, according to state TV. He said the foreigners came to Iran just two days before the Ashoura but did not specify their nationalities. Moslehi said cameras and equipment belonging to the foreigners was also confiscated. Iran has been conducting mass trials of opposition figures and activists arrested in the postelection protests. Five defendants have been sentenced to death and 81 had received prison terms ranging from six months up to 15 years. Authorities said more than 500 protesters were arrested after the Ashoura protests and that they would be put on trial. General prosecutor Gholam Hossein Mohseni Ejehi said those trials would be speedy and that some of the detainees could also face the death penalty over rioting against the ruling clerical establishment.