TEHRAN -- In central Tehran on Monday, demonstrators and authorities engaged in what has become a near daily cat-and-mouse routine: Protesters gathered in groups of several hundred shouting, "Death to the dictator." Iranian security forces chased them, waving batons and sticks, according to witnesses.

The security forces -- present in large numbers -- also used tear gas and fired gunshots into the air to scatter demonstrators. They easily dispersed the crowd, arresting men and women, dragging them away in handcuffs and loading them onto buses, witnesses said.

The protest was much smaller than recent demonstrations, and Monday appeared to mark the second day of relative calm in Tehran after security responded in force to demonstrations Saturday. Supporters of opposition candidates have staged more than a week of sometimes-violent protests since the declared victory of President Mahmoud Ahmadinejad in June 12 polls.

On Monday, Iran's Guardian Council, a top review panel responsible for investigating election disputes, said it had uncovered some irregularities in the polls, finding the number of votes in 50 districts exceeded the number of voters. The announcement, made on state-run media, was the first admission by authorities of voting irregularities.

Iranian officials said over the weekend that 10 to 13 people died in Saturday's violence, in addition to seven officially confirmed dead in the previous week and hundreds who have been injured.