"Those who damage public property, disrupt order and break the law must be responsible for their behaviour and pay the price", Interior Minister Abdolrahman Rahmani Fazli said on state television.
Two protesters were killed in the western province of Lourestan.
A young member of the Revolutionary Guards and a passer-by were also reported dead in towns near the cultural hub of Isfahan city, while TV had earlier confirmed the death of a policeman in nearby Najafabad, shot dead with a hunting rifle. "Unfortunately in these clashes two citizens from [the city of] Doroud were killed", he said.
Nasrollah Mohammadi, a mechanic near Tehran's Enghelab Square, the site of many past protests, said he supports the demonstrators' demands. At that time, the elite of the Islamic Republic was divided.
As reported, more than 100 people have been arrested during the night. Other videos have shown protesters peacefully demonstrating and welcoming police.
The UN Security Council was set to hold an emergency meeting on Friday afternoon to discuss the wave of protests in Iran, at the request of the United States.
It's important to remember that there is a connection between the Revolutionary Guard Corps and economics.
The protests began last Thursday in Mashhad over Iran's weak economy and an increase in food prices, and have expanded to several cities, with some protesters chanting against the government and the supreme leader, Ayatollah Ali Khamenei.
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The official, speaking on condition of anonymity, said Washington's main effort now was "trying to get a sense of who is mostly behind this, how large it is and does it have legs".
A protester from Tehran University told the Guardian by phone that although students were puzzled about how the protests were organised and spreading so quickly, they were not "getting leads from anyone".
Iran has faced small-scale demonstrations against economic hardship or local environmental crises in the last decade or so but the biggest crisis for the leadership was in 2009 when the country erupted in protests following disputed re-election of Ahmadinejad.
A more aggressive follow up could be to stretch the mullahs to the brink by ramping up military opposition to Iran's proxies in Syria, Lebanon, and Yemen. "That choice will ultimately determine the Islamic Republic's fate".
Anti-regime protests are going strong across Iran; from the big cities to rural areas, the Iranians want an end to the theocratic Regime that has held them hostage for nearly 40 years.
The Russian Embassy sent a message warning countries to stay out of Iran's affairs after President Donald Trump tweeted about the country's "repressed" people, as days of anti-government protests continued to unfold.
Telecommunications were disrupted on Saturday night and many people had intermittent problems accessing the internet.
With the failed promise of a quick recovery post the lifting of nuclear sanctions and cuts to subsidies, "It is no surprise. that the current protests in Iran have included slogans against investing resources in arenas outside of Iran", she said.
Unemployment in Iran is about 12 percent but among youth it reached 28.8 percent in 2017. Farnaz Asadi, a 31-year-old who sells goods via the popular messaging app Telegram, expressed anger at the government's decision to shut down the service after protesters used it to organize rallies and share photos and video.