CAIRO - Iranian authorities briefly detained the daughter of former President Akbar Hashemi Rafsanjani, the most powerful opposition supporter inside the country's clerical leadership, the official news agency reported.

Faezeh Hashemi, who has appeared at opposition protests in the past, was detained Sunday while trying to cause unrest by chanting anti-government slogans in one of the main streets of Tehran, the IRNA news agency said. Another pro-government news service reported that she was released a short while later.

Iran's opposition had called for rallies Sunday to mark a week since the deaths of two people in February 14 clashes between security forces and opposition protesters in Tehran. Hashemi's detention suggested crowds did attempt to gather Sunday, despite severe warnings from authorities.

One international rights group whose assessments have been right in the past said large numbers of protesters had turned out on major streets in the capital and four other cities. The New York-based International Campaign for Human Rights in Iran said security forces in Tehran dispersed the crowds with gunfire and tear gas. It said one person is believed to have been killed in the capital.

The report could not be independently confirmed, and Iran's police chief, Esmaeil Ahmadi Moghadam, denied there were any protests.

The rights group said witnesses reported crowds of protesters at key places in the capital: the main thoroughfare of Valiasr Street and in front of the state radio and TV building. It said it also had reports of demonstrations in the major cities of Mashad, Shiraz, Isfahan and Tabriz.

Last week's rally was called by opposition leaders Mir Hossein Mousavi and Mahdi Karroubi in solidarity with the Egyptian uprising. It was the largest demonstration by the opposition in more than a year. Both opposition leaders have been under house arrest since putting out the call for rallies.

The detention of Rafsanjani's daughter appeared to be another attempt to pressure the former president.

Iran's Fars news agency said she was released later Sunday after claiming she was out shopping, rather than joining protesters.

Hard-liners have harshly criticized the moderate Rafsanjani for supporting Mousavi in his election campaign challenge to President Mahmoud Ahmadinejad. Mousavi claims he was the rightful winner of the 2009 presidential election and that he was deprived of victory through fraud.

Those claims sent hundreds of thousands of pro-reform activists into the streets for months of demonstrations that mushroomed into a movement against Iran's ruling system. Authorities responded with a heavy crackdown and a mass trial of more than 100 activists and officials from previous pro-reform governments.

The ruling establishment came to see Rafsanjani as a serious threat, worrying that they had a dissenter within their ranks. There have been several attempts to sideline the former president, who is a powerful combination of elder statesman, super-wealthy tycoon and head of the only group empowered to remove Iran's supreme leader.

Besides accusing him of unspecified corruption, authorities have gone after his children.

His daughter, Faezeh, was also briefly detained along with four other family members days after the June 2009 election when she addressed a rally of hundreds of Mousavi supporters.

In November, an arrest warrant was issued for Rafsanjani's son, Mahdi Hashemi, on charges of fomenting the postelection unrest. The son, who has been living in Britain since shortly after the election, has denied the charges and is not known to have had any key role in the opposition movement or the street protests.