The UN said they had faced unfair trials based on forced confessions.

Protests swept across the country in September following the death in custody of Mahsa Amini, a 22-year-old woman who was detained by morality police for allegedly not wearing her hijab properly.

Authorities have portrayed them as "riots" and responded with force.

So far, at least 529 protesters have been killed and almost 20,000 detained, according to the Human Rights Activists' News Agency (HRANA). Four protesters have been hanged since December, while 107 others have reportedly been sentenced to death or charged with capital offences.

Footage posted on social media showed small protests took place on Thursday night in several parts of the capital, Tehran, as well as in nearby Karaj, the eastern city of Mashhad, the central city of Isfahan, the northern cities of Qazvin and Rasht, and the western cities of Arak, Izeh and Sanandaj.

In Karaj, a crowd chanted the names of Mohammad Mehdi Karami and Seyed Mohammad Hosseini, according to footage verified by BBC Persian. The two men were accused of killing a member of the paramilitary Basij force during a protest there in November.

Opposition activist collective 1500 Tasvir meanwhile shared a video from Mashhad in which a group of men and women are seen shouting: "My martyred brother, we shall avenge your blood."

Crowds were also filmed shouting slogans against Supreme Leader Ayatollah Ali Khamenei in the capital's Tehranpars district and in Rasht.

Kurdish rights group Hengaw posted footage that it said showed protesters burning tyres to block a main road in Sanandaj, which has been one of the epicentres of the unrest.

Although the street protests have subsided recently, activists frequently share videos in which people are heard chanting anti-government slogans at night-time or are seen spray-painting graffiti. Women also continue to be pictured refusing to comply with the strict hijab laws in public places.