But as rallies failed to materialize, a female protestor reached by ABC News by telephone in Tehran complained about the lack of leadership.
Asked whether she is disappointed that the streets were so quiet, the female protestor, who did not give her name, said "yes."
"Of course it is! It's really sad. People getting killed, people doing everything in their power to go against the regime after 30 years and we don't have the support here. We don't have proper leadership," she said.
The government's official statement is that the protests, sparked by the disputed presidential election of June 12, are being carried out by terrorists with links to foreign powers.
Speaking today, President Mahmoud Ahmedinejad demanded the United States and Britain stop interfering in Iran, adding that the election proved most Iranians love the regime.
That claim is proving more and more far-fetched on the ground. Today, the government continued mass arrests, including journalists, expelling BBC correspondent John Leyne from the country.
American Michelle May, who was in Iran on vacation, was unwittingly caught up in the violence. She said she was abducted by paramilitary basij fighters, the most aggressive in battling the protesters, and said she was accused of being a spy.
"I thought, maybe I'll make a scene and they'll go away," May said. "But they didn't. They put me into their car."
"I couldn't believe what was happening to me," she said.
Before releasing her, police forced her to sign a confession.
Even though the streets were quiet, the political battle persists at the highest levels of the Iranian government.
Today, the daughter of former President Hashemi Rafsanjani, Mousavi's chief political backer, was arrested. And Ali Larijani, the powerful parliament speaker, directly challenged the ruling Guardian Council for ignoring the protesters' complaints.
Faezeh, Rafsanjani's daughter, had joined protest crowds on Saturday, a day after Iran's Supreme Leader Ayatollah Ali Khamenei reiterated that such demonstrations would be considered criminal.
"Ayatollah Khamenei is not tolerating anybody who criticizes his policy. The main thing that is common among those arrested is that they have criticized the Ayatollha Khamenei over the past 20 years -- his foreign policy, his domestic policy, his cultural policy," said Mehdi Khalaji, a visiting fellow at the Washington Institute for Near East Policy.
"The government wants to cut the head of this movement from its body by cutting off all sources of information," Khalaji said.
Stateside, Iranian Americans marched today in support of opposition leader Mir Hossein Mousavi's movement, from Los Angeles and New York to the president's front door.
In Washington, D.C., the president was monitoring the situation closely.
An administration source said President Obama has received intelligence updates throughout the day.
Analysts say that the Iranian elections have posed a delicate diplomatic balancing act for this administration. If the clashes continue between the Iranian regime and the protestors, Obama could be forced to take an even stronger stance, they say.
As part of a broad crackdown on the media and perceived dissidents, the Iranian government has arrested 23 journalists and bloggers since the disputed presidential election on June 12.
A spokesman for Mousavi said today more than 700 supporters and organizers have also been detained over the past week, among them former Vice President Mohammed Ali Abtahi and Ebrahim Yazdi, a former foreign minister and architect of the Islamic Recpublic.
The official death toll in the often violent clashes between police and demostrators is 17, but many observers have suggested that the true count is much higher.
Iranian state television today announced the arrest of Faezeh Hashemi Rafsanjani and four other family members of a powerful former president, Ali Akbar Hashemi Rafsanjani.
Also today, Newsweek Magazine announced the arrest of staff reporter Maziar Bahari, a Canadian national who has lived in Iran and reported on the country for the past decade. Newsweek issued a statement saying Bahari was held without charge.
"Newsweek asks that world governments use whatever influence they have with the governemnt in Tehran to make clear that this detention is unwarranted and unacceptable, and to demand Mr. Bahari's release," the statement said.
Ali Mazroui, head of the Association of Iranian Journalists, was also arrested this morning.
Also among the detainees is journalist and women's rights advocate Jila Baniyaghoob. According to the non-governmental organization Reporters Without Borders, she and her husband, journalist Bahaman Ahamadi Amoee, were arrested by plainclothes intelligence forces at midnight on June 20.
Baniyaghoob is a winner of the Courage in Journalism award of the International Women's Media Foundation. She has spent a large portion of career advocating for women's rights in Iran and throughout the Middle East.
Before her detention, she was editor-in-chief of the online newspaper Kanoon Zanon Irani, literally "Focus on Iranian Women."
Throughout the unrest set off by the disputed election, Iran has restricted foreign journalists from covering opposition protests on the ground. ABC News cameras were seized last week.
The Tehran offices of Al Arabiya, a Saudi-owned network based in Dubai, were suspended until further notice.
In 2008, Iran was ranked number 166 out of 173 countries in press freedom index compiled by Reporters Without Borders. The organization described journalism in Iran as "a high risk exercise involving endless frustration and constant police and judicial harassment."
Confrontations were reported in the Iranian cities of Tehran, Shiraz, Esfahan and Rasht, as riot police and members of a religious militia known as the Basij cracked down on protests declared illegal by the state. They were chronicled by street-level observers and echoed around a world watching online.
Early Sunday, supporters of Mir Hossein Mousavi, whose alleged presidential election defeat a week ago touched off the protests, told ABC News they were planning new protests and hoping to shut down Tehran's main market, known as the bazaar.
State television has referred to the protesters as "terrorists," and allowed little information about the rallies to reach domestic viewers.
"It feels like a bad movie, as though everyone is pretending that yesterday did not happen," said one person in Tehran in an e-mail to ABC News.
Given foreign media restrictions in Iran, it remained difficult to confirm details of the weekend's violence. The BBC estimated tens of thousands of protesters were in the streets on Saturday.
As one crowd made its way toward Tehran's Revolution Square, reports said, it found the square closed off by security forces, including Revolutionary Guard forces and plainclothes members of the Basij militia. Those forces, bystanders said, assaulted protesters and chased them through the streets.
"This is a very unfair fight. They are using chains, hoses, clubs, they are carrying shotguns ... and they are brutal," one eyewitness in Tehran told ABC News in the midst of the clashes.
An amateur video posted to YouTube apparently showed the shooting death of one protester; sources said she was shot in Amir Abad, a neighborhood in Tehran.
Witnesses speaking with ABC News by e-mail described the clashes as a "street war."
"War is going on," one witness said, another describing "tear gas and burning trash cans everywhere."
"I feel like I'm in a police state for the first time. ... As of late afternoon, Basij are everywhere," said another protester, as the force was seen violently breaking up protests.
The International Campaign for Human Rights in Iran said forces pursued the wounded and arrested them in Tehran hospitals.
Justin McMahan, an American traveling through Iran with his wife when the protests began last week, was staying at a hotel near Engelab Square and saw the violence.
"We saw people getting indiscriminately clubbed by the Basij, beaten with batons, though they weren't wearing any green," he told ABC News. "There was unbelievable tension in the city, it was a place in turmoil. You could feel the society is deeply divided."
"There was talk of around 3,000 people were in Engelab Sq., said McMahan's wife Andrea. "We saw hundreds of military and Basijis in plainclothes.
"There were women screaming, gunshots fired," she added. "Police were brutally beating people, it was totally chaos. And it was hard to get any info. State TV stations were playing sports games."
By night protests had taken on a different form, channeled into what have become nightly neighborhood chants on city rooftops.
"The shouts of Allaho Akbar in holy city of Mashhad are 'explosive,'" said one source, "loudest it has ever been."
Others describe the chanting and shaking as "surreal."
The rooftop "Allaho Akbars," meaning "God is great," were widely as a means of protest during the 1979 Islamic Revolution. Sources said the practice has again become popular, given its relative safety -- largely out of reach of riot police in the streets.
The protesters directly defied Iran's highest authority, Supreme Leader Ayatollah Ali Khamenei, who in a Friday prayer speech called on them to stop demonstrating and accept President Mahmoud Ahmedinejad's reelection.
One week earlier, Ahmedinejad was declared the winner in a presidential ballot that gave him a commanding, some said implausible landslide win. Khamenei's speech warned that opposition leaders would be responsible for the consequences of any demonstrations, which some analysts saw as a veiled threat of violence.
The most prominent figure pushing back on Khamenei has been Mousavi, a pro-reform centrist and former prime minister who ran for president and claimed he beat Ahmedinejad. Mousavi has become the figurehead of the opposition movement, rallying a broad mass of supporters and showing up at Saturday's protests despite heavy restrictions on his movement.
Mousavi attended Saturday's chaotic rally in Tehran, vowing to challenge the official election results, instructing supporters to go on strike if he was arrested and expressing his willingness to die for his cause.
"I am prepared for martyrdom," Mousavi said on his Twitter and Facebook pages.
President Barack Obama spoke out on the events, telling the Iranian government "the world is watching."
"We mourn each and every innocent life that is lost," Obama said in a written statement. "We call on the Iranian government to stop all violent and unjust actions against its own people."
The election and its aftermath have complicated Obama's efforts at new diplomacy between the United States and Iran, which would break 30 years of strained ties and antagonism.
Supporters of Mir-Hossein Mousavi have called on the United States and other countries not to recognize Ahmedinejad's election win.
Obama has said outreach efforts would continue, though it would be difficult to do so without at least tacitly acknowledging Ahmedinejad's second term.