TEHRAN, Iran (CNN) -- A group of 20 to 30 men, carrying clubs and metal pipes, banged on the door of an apartment building in a Tehran neighborhood.
Fresh clashes broke out Sunday between police and protesters in Tehran.
The group was agitated. They chanted and shouted and kept banging on the building's door. Inside, they suspected, was a person who had chanted a slogan against President Mahmoud Ahmadinejad.
This scene was witnessed by CNN reporters in Tehran on Sunday. But in the confusion and controversy that has followed Ahmadinejad's re-election, many stories like this have been told through social networking Web sites such as Twitter -- despite reports that the Iranian government has clamped down on such services and mobile phones.
The scene was just one involving both sides of the heated debate after Friday's election.
The landslide defeat of Ahmadinejad's leading opponent, Mir Hossein Moussavi, who some analysts predicted would win the election, triggered angry protests in Iran and other cities around the world. Watch how the world is reacting to the elections »
The protests also appeared to trigger a counterreaction from supporters of Ahmadinejad, tens of thousands of whom rallied in central Tehran on Sunday.
"I'm seeing something that I've never seen before," one Moussavi supporter told CNN earlier in the day. "Young people are getting abused, sabotaged, hit with batons."
The Moussavi supporter, whose name CNN is concealing for security reasons, reported hearing gunshots and seeing men in plainclothes breaking windows.
Meanwhile, Iranian media has mostly ignored the protests and international journalists have been prevented from covering the demonstrations. The Islamic republic has ordered the Dubai-based satellite network Al-Arabiya's Tehran bureau shuttered for a week.
Ahmadinejad told a crowd of tens of thousands of supporters Sunday that Iran's elections are "the soundest, the healthiest of their kind." And he told reporters his country had a free press, and people "can say whatever they like."
Moussavi's supporters say the election was rigged. But the huge turnout for Ahmadinejad's victory speech Sunday leaves no doubt that the president carries plenty of support.
The streets of Tehran were crowded Sunday with supporters and detractors of Ahmadinejad, as protests and clashes continued for the second day after his re-election. Protesters lit tires and garbage on fire and crowds milling on the streets, blocking traffic.
Before the victory rally, however, riot police fired tear gas and brandished batons to disperse about 100 stone-throwing protesters from the site of his address.
There were reports of clashes between police and protesters, but many of the injuries were being blamed on groups of Ahmadinejad supporters -- who wore nothing identifying them as police -- who chased Moussavi supporters, as CNN witnessed.
"It's horrific, shameful and paradoxical to what you see on TV," the Moussavi supporter said. Watch Moussavi supporter express anger »
The divide was also seen in cities outside Iran with significant Iranian expatriate populations. Many Iranians overseas sent in absentee ballots, and the overwhelming sentiment among the demonstrators was their votes had not been counted.
Protests in Washington; London, England; Toronto, Canada; Berlin, Germany; and Los Angeles, California, each drew several hundred people. All of them were seemingly anti-Ahmadinejad. See protests around the world »
Roja Bandari, a University of California student who wore a neckerchief of the green adopted by Moussavi's supporters, said the demonstrators "wanted to come out and say there are supporters of the reformists everywhere."
"All the polls and all the predictions were saying that Moussavi was going to win, and Ahmadinejad won with such a landslide, which was something that no one even thought about," Bandari said. "Even Ahmadinejad supporters didn't think about that. And then the way that they gave out the news was very fishy."
In Washington, about 150 protesters stood outside the Iranian Interests Section for the second day in a row, waving Iranian flags and holding posters demanding votes be accurately counted.
"This is all grassroots. This is not anything that is particularly recognized. There's no political party. There's no political agenda," said protester Babek Talabi. "These are Iranian-Americans, Iranians around the world who cast their votes and stand with Iranians in Iran and want their votes counted,"
Police gave the protesters a warning to disperse from the area after local businesses complained their entrances were being blocked. Protesters began marching down the street towards the Lincoln Memorial shortly after the warning.
CNN's Christiane Amanpour and Samson Desta contributed to this report.