Former Iranian detainee Roxana Saberi was one of the many protesters in the US called on Iran to end its clampdown on the Opposition movement on Saturday, demanding the release of hundreds of people who have been rounded up in demonstrations against the country's disputed June 12 election.
Groups including Human Rights Watch and Amnesty International backed a global day of action, with protests planned in more than 80 cities, including several in the United States.
The protesters want Iranian authorities to release what they say are hundreds, or even thousands, of people detained during protests that followed the presidential election last month that returned Mahmoud Ahmadinejad to power.
Inside Iran, as well, Iranian police and pro-government militia attacked and scattered hundreds of protesters who had gathered in Tehran in response to the global demonstrations of solidarity, witnesses said.
Demonstrators in Vanak and Mirdamad districts chanted "death to the dictator" and "we want our vote back" before they were attacked and beaten by police Saturday. The witnesses spoke on condition of anonymity for fear of retaliation.
Supreme Leader Ayatollah Ali Khamenei has already declared Ahmadinejad's victory valid. In the United States, several thousand people gathered in Los Angeles and San Francisco in rallies Saturday night.
At the University of California, Los Angeles, many wore green in solidarity with the Iranian protesters. Coordinator Elahe Amani said the protesters called for the United Nations to send a delegation to Iran in order to investigate the villence. Thousands more shouted "Free Iran" earlier Saturday in front of San Francisco City Hall.
Several hundred protesters assembled just off Times Square in New York City. One man hoisted a green placard, splattered with red, that read, "Where is my vote?" The crowd chanted, "Stop the killing. Stop the torture." A small group of Iranians in New York have been on a three-day hunger strike and are holding frequent demonstrations outside the United Nations to call on the world body to investigate human rights abuses in Iran.
In Washington, hundreds of demonstrators were marching from a U.N. office downtown to the National Mall for a rally.
Iranian-American journalist Roxana Saberi told some 200 protesters in Chicago that in Iran protesters could be beaten by authorities and then forced to sign a false confessions. Saberi was recently released by Iran after being convicted of spying for the U.S. in a case that drew widespread criticism of the Mideast state's justice system.
Police said about 600 protesters joined a "noisy but peaceful" demonstration, outside the Iranian embassy in London, one of a series of events in cities across Europe. In Brussels, Belgium, protesters held placards carrying images of the detained or dead, including Neda Agha Soltan, the 27-year-old whose death -- beamed around the world on the Internet -- became a rallying cry for opponents of the regime.
In Amsterdam, several hundred people watched Iranian Nobel Peace prize laureate Shirin Ebadi urge the international community to reject the outcome of the Iranian election and called for a new vote monitored by the United Nations.
About 80 people wearing headbands, wristbands or bandanas in green -- the colour of Iran's protest movement -- demonstrated in front of the UN's European headquarters in Geneva, while several hundred people staged a rally at Paris' Trocadero square overlooking the Eiffel Tower.
"We've had enough of religious regimes that don't have the Iranian people's best interest at heart," said protester Sakineh Davoodi, a 50-year-old cashier from Iran who has lived in France for 23 years.
About 350 people gathered in downtown Vienna, and about 150 protesters gathered in Rome. In Norway, about 250 Iranian emigres met at a conference center on the outskirts of Oslo, and about 3,000 people gathered in Stockholm and others in Copenhagen, Denmark.
In the Pakistani capital, Islamabad, some 20 Iranians -- among them refugees and students -- gathered outside the local press club to protest the Iranian crackdown, yelling "Death to the dictator!"
"Innocent Iranians are being killed," said Hessam Moghimi, 27, who has lived in Pakistan for about eight years. "We want justice for the blood that's been spilled."
There were small protests in the Australian cities of Sydney, Melbourne, Brisbane, Adelaide and the capital, Canberra. About 80 people gathered in Tokyo, draping green scarves around their necks and lighting candles.
In Seoul, South Korea, where about 30 people rallied, Amnesty's Park Jin-ok said the group was calling for "immediate and unconditional release" of detainees.
About 20 gathered in a small square in Sao Paulo, Brazil, to take part in a 30-minute rally. Fariba Vahdat, a member of Brazil's Baha'i community, said she attended to protest "the cruelty being meted out on the streets of Iran."
Dozens of activists gathered outside the embassy of Iran in Prague to protest the detention of those who protested election results in Iran. "The people could face torture and their lives are in danger," said Lenka Pitronova, an organizer of the rally.
The demonstrators also want the UN to investigate alleged rights abuses and say Tehran must allow freedom of expression and assembly. Hundreds of thousands of Iranians held protests after the election denouncing it as fraudulent until security forces launched a heavy crackdown, arresting hundreds and killing at least 20.
Track Latest News Live on NDTV.com and get news updates from India and around the world