The demonstrations began on December 28 near Tehran’s Grand Bazaar and later spread to several cities across the country.
Iran has also experienced widespread connectivity disruptions.
Internet monitoring group NetBlocks has said the country has been offline for more than 12 hours.
Iranian authorities have not released official casualty figures.
However, the Human Rights Activists News Agency said on Thursday that 2,277 people had been arrested, dozens injured and 42 killed, including eight members of the security forces.
Iranian officials have accused the United States and Israel of fomenting the unrest.
On Friday, authorities warned that security forces and the judiciary would show “no tolerance whatsoever toward saboteurs.”
Iran’s unrest has come as Trump is preoccupied with his abduction of Venezuelan President Nicolas Maduro and has been floating the possibility of acquiring Greenland by purchase or military force.
Trump ordered bombing raids on Iranian nuclear facilities last June and has warned he is prepared to do so again if Tehran tries to reconstitute the programme.
US to blame for ‘violent’ protests
US is to blame for “the transformation of peaceful protests into violent, subversive acts and widespread vandalism” in Iran, the country’s UN ambassador told the Security Council on Friday.
Iran condemns “the ongoing, unlawful, and irresponsible conduct of the United States of America, in coordination with the Israeli regime, in interfering in Iran’s internal affairs through threats, incitement, and the deliberate encouragement of instability and violence,” Iran’s UN Ambassador Amir Saeid Iravani wrote in a letter, seen by Reuters news agency.
He accused Washington of “destabilising practices” that undermine the founding UN Charter, violate fundamental principles of international law, and threaten the foundations of international peace and security.