Iran’s Revolutionary Guards have warned anti-government protesters they will face the nation’s “iron fist” if political unrest continues.
But a Revolutionary Guards commander said the protests had degenerated into people chanting political slogans and burning public property.
They are the biggest show of dissent since huge pro-reform rallies in 2009. There are reports of two deaths.
There were calls for the removal or death of Iran’s Supreme leader, Ayatollah Ali Khamenei, in the cities of Khoramabad, Zanjan and Ahvaz.
Iran’s Islamic Revolutions Guards Corp is a powerful force with ties to the country’s supreme leader, and is dedicated to preserving the country’s Islamic system.
Brigadier-General Esmail Kowsari told the ISNA news agency: “If people came into the streets over high prices, they should not have chanted those slogans and burned public property and cars.”
Iran’s interior minister has also warned the public that protesters will be held accountable.
“Those who damage public property, disrupt order and break the law must be responsible for their behaviour and pay the price,” Abdolreza Rahmani-Fazli said.
“The spreading of violence, fear and terror will definitely be confronted.”
Protests began in the north-eastern city of Mashhad on Thursday and spread to other major cities on Friday.
A small demonstration in Tehran grew to several thousand people on Saturday, and students clashed with police. The protests also became violent in several other towns.
BBC Persian correspondent Kasra Naji said a common factor in all locations has been protesters’ demand for an end to clerical rule in Iran.
There is also anger at Iran’s interventions abroad. In Mashhad, some chanted “not Gaza, not Lebanon, my life for Iran”, a reference to what protesters say is the administration’s focus on foreign rather than domestic issues.
Iran is a key provider of military support to the government of Bashar al-Assad in Syria. It is also accused of providing arms to Houthi rebels fighting a Saudi-led coalition in Yemen, which it denies, and is an ally of Lebanon’s powerful Shia movement Hezbollah.
The Iranian authorities are blaming anti-revolutionaries and agents of foreign powers for the outbreak.
Also on Saturday, thousands of pro-government demonstrators turned out for pre-arranged rallies to mark the eighth anniversary of the suppression of the 2009 street protests.
President Donald Trump tweeted: “Oppressive regimes cannot endure forever, and the day will come when the Iranian people will face a choice. The world is watching!”
Iran’s foreign ministry called earlier comments from Mr Trump and other US officials “opportunistic and deceitful”.