Street protests hit Iran for a third day running, spreading to the capital Tehran with crowds confronting police and attacking state buildings.
Social media reports say at least two demonstrators had been shot dead in a provincial town.
The wave of anti-government demonstrations, prompted in part by discontent over economic hardship and alleged corruption, are the most serious since months of unrest in 2009 that followed the disputed re-election of then-President Mahmoud Ahmadinejad.
Saturday’s protests coincided with state-sponsored rallies staged across the Islamic Republic to mark the final suppression of the 2009 unrest by security forces, with mass pro-government events in Tehran and Mashhad, Iran’s second city.
Pro-government rallies were held in some 1,200 cities and towns in all, state television reported.
At the same time, anti-government demonstrations broke out anew in a string of cities.
In Tehran, until now untroubled by anti-government demonstrations, protesters confronted and stoned riot police around the main university, with pro-government crowds nearby.
Videos posted on social media from the western town of Dorud showed two young men lying motionless on the ground, each covered with blood. A voiceover said they had been shot dead by riot police.
Other protesters in the video chanted, “I will kill whoever killed my brother!” The video, like others posted during the current protest wave, could not be immediately authenticated.
In earlier footage, marchers in Dorud shouted, “Death to the dictator,” referring to Supreme Leader Ayatollah Ali Khamenei.
Social media video from Mashhad showed protesters overturning a riot police car and police motorcycles set ablaze.
In Tehran, the semi-official news agency Fars said up to 70 students gathered in front of its main university and hurled rocks at police, also chanting, “Death to the dictator.”
Social media footage showed riot police using clubs to disperse more protesters marching in nearby streets, and arresting some of them. The student news agency ISNA said police shut two metro stations to prevent more protesters arriving.
In Tehran and Karaj west of the capital, protesters smashed windows on state buildings and set fires in the streets.
Images carried by the semi-official news agency Tasnim showed burning garbage bins and smashed-up bus shelters in the street lining the university after the protests subsided.
The United States condemned the scores of arrests of protesters reported by Iranian media since Thursday.
President Donald Trump tweeted, “The entire world understands that the good people of Iran want change, and, other than the vast military power of the United States, that Iran’s people are what their leaders fear the most.”
State media quoted Foreign Ministry spokesman Bahram Qassemi as saying in response to an earlier Trump tweet criticising the arrests: “The Iranian people see no value in the opportunistic claims by American officials and Mr. Trump.”