Witnesses in Iran's capital say police officers dispersed a group of a few hundred protesters who started to gather Monday.
The opposition demonstrators had gathered at Haft-e-Tir Square in central Tehran, in the face of a heavy police presence. According to some witnesses, police used tear gas to disperse the crowd.
Earlier Monday, the country's elite Revolutionary Guard warned it would use force to break up protests.
Iranian state radio reported earlier that at least 457 people were arrested Saturday -- a day marked by clashes between security forces and demonstrators that resulted in the deaths of at least 10 people.
Iran's official death toll from post-election violence now stands at 17. Other reports say the toll is considerably higher. None of the reports has been confirmed, and Iran has barred independent media from reporting in the country.
Defeated candidate Mir Hossein Mousavi issued a statement supporting further protests against President Mahmoud Ahmadinejad's June 12th victory, but he urged restraint.
Meanwhile, Iranian media are reporting that Iran's Guardian Council has said voter irregularities have been documented in dozens of cities.
Iran's Press TV says the Council's spokesman made the comment Sunday on Iranian television. The spokesman said the total number of votes in 50 cities surpasses the number of people eligible to cast ballots there, and more than three million votes could be in question.
But the spokesman also said the Guardian Council has not yet determined whether the election's outcome was actually affected. And he denied defeated candidates' allegations that such an irregularity occurred in more than 80 cities.
The disputed vote has triggered Iran's greatest unrest since the 1979 Islamic Revolution.