Witnesses in the Iranian capital say riot police with batons and shields have dispersed a crowd of a few hundred people who tried to gather near the parliament building in Tehran for another post-election protest.
Residents in Iran say the government has maintained a heavy police presence in the streets, especially since Saturday's violence between authorities and protesters killed at least 10 people.
Iran's Revolutionary Guard has warned it will use force to crush demonstrations. People have used social networking Web sites to call for rallies, but recent attempts have not even come close to the hundreds of thousands of Iranians who took to the streets last week.
Iran's supreme leader, Ayatollah Ali Khamenei, said again Wednesday that the country will not yield to pressure over the June 12 presidential election, in which the incumbent, Mahmoud Ahmadinejad, was declared the winner.
In the face of violent suppression, witnesses say many opposition supporters take to their rooftops in a nightly ritual to shout "Allahu akbar" -- God is Greatest, a tactic also used during Iran's Islamic Revolution 30 years ago.
Western nations have criticized Iran's government for its violent response to demonstrations.
The disputed vote has triggered Iran's greatest unrest since the 1979 revolution, and the government has created a special court to try the hundreds of Iranians it has arrested in the post-election turmoil.
Iran's official death toll stands at 17, but witnesses to clashes between protesters and security forces put the toll much higher. Figures cannot be verified because Iran has severely restricted news organizations' abilities to report from the country.
Opposition protesters say Iran's presidential vote was rigged. They cite numerous alleged instances of election fraud, among them a contention that the reported margin of victory for President Ahmadinejad over reformist challenger Mir Hossein Mousavi was impossibly high. Iran's Guardian Council has admitted finding voter irregularities in 50 districts.
The council says it will continue to investigate polling complaints beyond Wednesday's set deadline (until June 29th), but it has ruled out overturning the results.