TEHRAN, Iran - Government opponents shouted "Allahu Akbar" and "Death to the Dictator" from Tehran's rooftops in the pouring rain on the eve of student demonstrations planned for today. Authorities choked off Internet access and warned journalists working for foreign media to stick to their offices for the next three days.

The measures were aimed at depriving the opposition of its key means of mobilizing the masses as Iran's clerical rulers keep a tight lid on dissent. Government opponents are seeking, nonetheless, to get large numbers of demonstrators to turn out today and show that their movement still has momentum.

Opposition leader Mir Hossein Mousavi threw his support behind the student demonstrations and declared that his movement is still alive. A statement posted on his Web site said that the clerical establishment cannot silence students and was losing legitimacy in the Iranian people's minds.

"A great nation would not stay silent when some confiscate its vote," said Mousavi, who claims that President Mahmoud Ahmadinejad stole the June 12 election victory from him by fraud.

Supreme Leader Ayatollah Ali Khamenei, who has final say on all state matters, accused the opposition yesterday of exposing divisions in the country and creating opportunities for Iran's enemies.

Iran's universities have been strongholds of the opposition movement that grew out of the disputed election, and authorities have besieged campuses nationwide with a wave of arrests and student expulsions. The pro-government Basij militia has also recruited informers on campuses to blow the whistle on any opposition troublemakers, according to students.