According to eyewitness reports, Iranian police Monday attacked hundred of demonstrators attending an opposition rally in a Tehran square with tear gas.
Demonstrators had gathered on Haft-e Tir Square despite the warning from Iran's Revolutionary Guards against holding unapproved rallies.
Earlier, defeated presidential candidate Mir Hossein Mousavi urged his supporters to continue demonstrating, but "with restraint."
"The country belongs to you," Mr. Mousavi told supporters on his Web site Kalam, adding that "it is your right to protest lies and fraud," in reference to disputed election results which gave a landslide victory to incumbent Mahmoud Ahmedinejad.
Iran's Revolutionary Guards, however, vowed to crush further protest rallies, telling opposition supporters to be ready for a "revolutionary confrontation" if they continue to demonstrate.
Iran analyst Mehrdad Khonsari with the London-based Center for Arab and Iranian Studies says that government tactics to quell demonstrations is having limited results.
"The authorities are succeeding in trying to prevent a mass congregation in one place, which means they're stopping people coming to a central location or a central point from various avenues, but they have not succeeded in preventing people from coming out, so instead they're trying to control the crowds arriving at that central point from a number of other streets and locations," said Khonsari. "This tactic has been successful in preventing huge numbers from gathering in one place, but this does not mean that the demonstrations have fizzled out or that people have lost their enthusiasm."
He also notes that there are similarities between the period leading up to the 1979 Islamic Revolution and events of today.
"There are similarities in appearance, but what separates the two is that the government at that time did not have the resolve to want to quell the rebellion at any price, and the Shah was seeking to make compromises with the opposition," he continued. "This time, the regime is bent on quashing the rebellion, and they don't want to make any compromises, whatsoever. Finally, the revolution was sort of aimed at opposing forces of modernity in favor of traditional religious values. This time, you see the forces of modernity challenging conservative religious forces."