While scattered economic protests have occurred in the past, overtly political protests are rare in Iran, where security services are omnipresent.
The semiofficial Iranian Labor News Agency quoted Mohsen Nasj-Hamedani, Tehran’s deputy governor-general for security affairs, as saying that “a number of protesters” were arrested in Tehran on Friday after “an illegal call” for a rally.
Mr. Hamedani warned that “such gatherings will be firmly dealt with by the police.”
The Revolutionary Guards, which along with its Basij militia spearheaded a crackdown against protesters in 2009, said in a statement carried by state news media on Saturday that there were efforts to repeat that year’s unrest, but warned that Iran “will not allow the country to be hurt.”
Some social media users called for more antigovernment rallies in Tehran and other cities later Saturday. But the government called for an end to “illegal” gatherings. The Associated Press reported that hundreds of students had joined a protest at Tehran University on Saturday, citing witnesses who said they had seen a mass of riot police officers at the gates of the university. Some nearby streets were blocked off.
President Trump tweeted support for the protesters who had turned out in major Iranian cities, saying the government should respect the people’s right to express themselves.
“The world is watching!” Mr. Trump said.
The State Department also expressed support for the protesters. “The United States strongly condemns the arrest of peaceful protesters,” it said in a statement. “We urge all nations to publicly support the Iranian people and their demands for basic rights and an end to corruption.”
At the government-sactioned rally on Saturday, one demonstrator, Ali Ahmadi, 27, blamed the United States for Iran’s economic problems, according to The A.Press.
“They always say that we are supporting Iranian people, but who should pay the costs?” he said.
President Hassan Rouhani won re-election this year on promises to revitalize an economy hit hard by international sanctions. But the cumulative effect of those sanctions and decades of government mismanagement have taken their toll on the economy.
The nation’s unemployment stood at 12.4 percent this fiscal year, according to the Statistical Center of Iran, up 1.4 percentage points from the previous year. Of a population of 80 million, about 3.2 million Iranians are jobless. Unemployment among young people stands at more than 40 percent.
The unauthorized protests began on Thursday in Mashhad, a city of two million in the northeast that is one of the holiest places in Shiite Islam. Iranians there denounced recent price increases in particular and the moribund state of the economy in general, according to local news agencies.
Vice President Eshaq Jahangiri, a reformist ally of the president, said that hard-line conservative opponents of the Mr. Rouhani might have galvanized the protests but lost control of them.
“Those who are behind such events will burn their own fingers,” state media quoted him as saying.
On Friday, the police dispersed antigovernment demonstrators in the western city of Kermanshah as protests spread to several cities. On Thursday, the police arrested 52 people, according to a judicial official in Mashhad.
State television said rallies were scheduled to be held in more than 1,200 cities and towns on Saturday.