Iranian protesters chanted political slogans under the eye of security forces during a memorial on Thursday for a man killed in demonstrations last month, videos on social media showed.
The images showed one woman shouting "Death to the dictator" as people around her ran in the cemetery in the city of Karaj.
Other videos showed a helicopter flying nearby and security forces around the cemetery.
Social media postings said some protesters were arrested at the ceremony for 27-year-old Pouya Bakhtiari but Reuters could not confirm that.
Ceremonies also took place in a handful of other cities to honour those killed in recent protests, videos showed.
Demonstrations against a hike in fuel prices turned political last month, sparking the bloodiest crackdown in the 40-year history of the Islamic Republic.
About 1,500 people were killed during less than two weeks of unrest, three Iranian interior ministry officials told Reuters, though international rights groups put the figure much lower and Iran called the report "fake news".
Mr Bakhtiari’s parents were arrested on Monday after refusing to call off the ceremony at the cemetery where he was buried, according to the Centre for Human Rights in Iran (CHRI), a New York-based advocacy group. Mr Bakhtiari died of a bullet wound to the head in Karaj on November 16, it said.
In a report on Tuesday, the semi-official Mehr news agency noted that Mr Bakhtiari had been “killed in a suspicious way”.
Iranian authorities had been on high alert for potential protests on Thursday and restricted mobile internet access in several provinces, an Iranian news agency reported on Wednesday.
Internet blockage observatory NetBlocks said on Thursday some mobile networks in Iran were down to only five per cent of normal capacity.
"Mobile internet connectivity has fallen further in Iran amid reports of security reinforcement; real-time network data show connectivity at 5 per cent of ordinary levels on specified networks after four distinct cuts; incident ongoing," it said on Twitter.
Police chief Hossein Rahimi said there were no security incidents in Tehran on Thursday, according to the semi-official Tasnim news agency.
Iran has blamed "thugs" linked to exiles and foreign countries including the United States, Israel and Saudi Arabia, for stirring up unrest through social media.