Iran's Revolutionary Guard has warned of "decisive" action if protests in the country continue.
At least five people were killed in the rioting, which began on Friday after the announcement of fuel rationing and a 50% increase in gasoline prices.
At least 100 banks, buildings and cars were set on fire, according to state media.
Iranian authorities closed the internet on Saturday, but online video sharing earlier contained gunshots and pictures of severely injured people.
In a statement, the country's main security force said: "If necessary, we will take decisive and revolutionary measures against any continuous movement to disrupt the peace and security of the people."
Fars, a semi-official news agency in Iran, said there were more than 87,000 protesters across the country and about 1,000 were arrested.
The streets were supposedly calmer on Monday and General Gholamreza Soleimani, chief of Iran's Basil paramilitary Revolutionary Guards, insisted that security forces acted with "restraint and patience."
A gas station in Eslamshahr near the Iranian capital of Tehran has been hit.
Iran is home to the world's fourth largest oil reserve and cheap oil is almost seen as a birthright, but even that has not saved the economy from the trouble.
Since US President Donald Trump withdrew his country from the 2015 nuclear deal last year and imposed sanctions, jobs have become scarce and the currency has collapsed.
When the nuclear deal was struck, Iran's rial was trading at $ 32,000 to $ 1, but it worsened to more than $ 123,000 to $ 1.
Sky News diplomatic editor Dominic Waghorn said: "The Iranian government claimed that US sanctions were uniting the people behind them, but these scenes (of the protests) suggest a different story."
Parliamentary elections are scheduled for February and the unrest, the worst since 2017, will be another challenge for President Hassan Rouhani.
Rouhani said raising the price of gasoline would help raise money for donations to 18 million families struggling with families starting this week.
US Secretary of State Mike Pompeo said he was monitoring the protests and was deeply concerned about reports of deaths.
But Iranian Foreign Minister Mohammad Javad Zarif responded: "A regime that prevents food and medicine for ordinary people, including the elderly and sick, from economic terrorism can never escape the obscene claim of supporting the Iranian people."