Iran has arrested the daughter of reformist ex-President Akbar Hashemi Rafsanjani for taking part in a banned protest march, state media reports say.
Faezeh Hashemi Rafsanjani was held in Tehran while "making blunt statements and chanting provocative slogans", said the official news agency Irna.
She has been held several times before for opposition-related activity.
Iran has seen a number of opposition protests since the wave of unrest began in north Africa earlier in the year.
Iran's opposition Green movement had called for a day of demonstrations for Sunday.
Activists reported that groups of protesters had managed to gather in a number of places in Tehran, including outside the headquarters of Iran's state broadcaster.
But Iran's authorities appear to be determined to make sure that any protests are contained and stopped, says the BBC's Tehran correspondent James Reynolds, reporting from London.
Some journalists had been warned by the government not to go out into the streets to cover any unrest.
In some places access to websites has been blocked. Reports say that police wearing anti-riot gear have been deployed in the centre of Tehran.
Last Monday thousands of opposition members rallied for the first time in more than a year. Two people were killed during the protests.
Further clashes broke out on Wednesday during the funeral of one of the people killed on Monday.