Protests over gasoline prices have swept across some 100 cities and towns in Iran, turning violent faster than widespread economic protests in 2017 and rallies over the country’s disputed 2009 presidential election.

Read: Iran moves on ultra-cheap petrol

The scale of the unrest that began on Friday remains unclear as authorities have shut down the internet across this nation of 80 million people.

Prior to that, online videos purported to show people abandoning their cars on major highways and marching on city centres. Demonstrations devolved into violence as rioters set fire to gas stations, attacked banks and robbed stores.

While sparked by President Hassan Rouhani’s decision to raise government-set gasoline prices, the protests take root in decades-old economic problems, exacerbated by the US pullout of Iran’s nuclear deal with world powers and re-imposed economic sanctions.

And though some protest chants directly challenge Iran’s Shia theocracy, its government has the manpower — and experience — to quickly put down demonstrations.

Putting out fire with gasoline

For Iranians, cheap gasoline is practically considered a birthright. Iran holds the world’s fourth-largest crude oil reserves. As jobs remain scarce, many Iranians work as informal taxi drivers. But subsidising prices both benefited Iran’s wealthy and spurred gasoline smuggling to neighbouring countries.

The International Energy Agency estimates that Iran spent more than any other nation in the world to subsidise fossil-fuel costs in 2018 — $69 billion in total. Over $26 billion went toward oil subsidies, the IEA said.

Previous pushes to cut the subsidies sparked protests, so Rouhani's government changed prices early on Friday — at the start of the weekend in Iran — with no warning. The new prices are seeing consumers pay 13 cents a litre (49 cents a gallon) on their first 60 litres a month. After that, they pay 26 cents a litre (98 cents a gallon).

Even with those hikes, Iran remains one of the cheapest places in the world to buy gasoline. A gallon of regular unleaded gasoline costs on average $2.59 in the US, according to AAA.

Demonstrations quickly escalate in Iran

Since the price hike, demonstrators have abandoned cars along major highways and joined mass protests in the capital, Tehran, and elsewhere. Some protests turned violent, with demonstrators setting fires as gunfire rang out.

It remains to be seen how many people were arrested, injured or killed. Iranian authorities on Sunday raised the official death toll in the violence to at least three. However, that figure may be low. Videos from the protests have shown people gravely wounded.

Read: 106 protesters killed over past five days in Iran: Amnesty

London-based rights group Amnesty International has said more than 100 demonstrators were believed to have been killed across Iran since security forces were ordered to "crush" the protests.

The semiofficial Fars news agency, close to the country’s Revolutionary Guard, reported Sunday that demonstrators had ransacked some 100 banks and stores in the country. Authorities arrested some 1,000 people, Fars reported, citing unnamed security officials for the information.

Communication breakdown

Part of the reason it remains difficult to know what’s happening in Iran is because authorities have shut down access to the internet. Since late Saturday night, access went from worse to nonexistent across the nation. That stopped the spread of online videos of the demonstrations and affected the ability of protesters to share information.

The group NetBlocks, which monitors worldwide internet access, said connectivity had fallen to just 7 per cent of ordinary levels.

It called Iran’s shutdown the most severe "in terms of its technical complexity and breadth".

The internet firm Oracle called it "the largest internet shutdown ever observed in Iran".

Some local websites, like those of state media outlets, remains accessible, but Iran’s window to the outside world largely has closed. The Trump administration has criticized the shutdown.

Economic woes

Iran has suffered economic problems since its 1979 Islamic Revolution cut off its decades-long relationship with the US. Its eight-year war with Iraq in the 1980s followed, further straining the economy. While its oil industry remains a lifeline for government revenues, sanctions have long affected its ability to work on improvements and upgrades to keep production high.

The collapse of the nuclear deal has exacerbated those problems ever since President Donald Trump unilaterally withdrew America from the accord over a year ago. The Iranian rial, which traded at 32,000 to $1 at the time of the accord, now trades around 123,000 to $1. That has destroyed people’s savings, forcing them to invest in physical assets or real estate. Iran has since begun breaking terms of the deal as it tries to force Europe to come up with a way to allow it to sell crude oil abroad despite American sanctions.

Crackdown looms

It appears that Iran’s government is preparing to crackdown on the demonstrators. State television has begun airing segments focusing on violent attacks in the protests.

Supreme Leader Ayatollah Ali Khamenei made a point to refer to "thugs" in comments he made on Sunday to try to calm the public.

Iranian authorities have had much experience in dealing with public unrest, whether in student protests that swept Iran in 1999, the Green Movement demonstrations that followed widespread allegations of vote rigging in Iran’s 2009 presidential election or the economic protests that began at the end of 2017.

Online videos showed uniformed police officers trying to talk crowds into dispersing. Later, anti-riot police entered the streets. Plainclothes security forces, wielding bats and clubs, have been seen on the streets of Tehran. Videos also showed the motorcycle-riding members of the Basij, the all-volunteer arm of Iran’s paramilitary Revolutionary Guard.

Because of that, the US-based private intelligence firm Stratfor notes Iran has developed tools like security force crackdowns and information control. "This makes it unlikely that the fuel protests will grow to the point of upending the Iranian political environment," it said.

Rouhani claims victory

On Wednesday, Rouhani claimed victory over unrest he blamed on Iran’s foreign enemies, according to state media, after protests over an increase in gasoline prices last week that have shaken the country.

"The Iranian people have again succeeded at a historic test and shown that they will not let enemies benefit from the situation, even though they might have complaints about the country’s management," Rouhani said in remarks carried by the state broadcaster IRIB on its website.

Meanwhile, Iran's Supreme leader Ayatollah Ali Khamenei said the enemy had been "repelled" in the country.

The United Nations called for restraint on Tuesday and voiced alarm at reports dozens may have been killed in the violence.

Saudi Arabia’s King Salman urged arch-rival Iran to abandon an expansionist ideology that has "harmed" its own people, following the violent street protests in the Islamic republic.