(CNN) Iran's Interior Minister Abdolreza Rahmani Fazil has said security forces will act against those protesting a nationwide increase in gas prices if the "vandalism" continues, according to state-run Press TV.

Demonstrations erupted in several cities across the country Friday following Thursday's announcement by Iran's National Oil Company (NIOPDC) of at least a 50% increase in gas prices.

"Several" people have died in the protests, Iran's Supreme Leader Ayatollah Seyyed Ali Khamenei , said in a speech Sunday.In the province of Sirjan at least one person has been killed, the region's government has said.

More than 1,000 protesters have been arrested across the country, according to the semi-official Fars News Agency. In Esfehan, 15 gas stations were stormed and set on fire.

Videos published by official Iranian media show protesters blocking main roads and causing traffic jams.

But journalists in Iran and international news agencies report the situation is much worse, citing clashes between protesters and riot police, damage to public property, and tires and garbage burning on the ground. Gunshots were also heard.

Press TV reported that Rahmani Fazli has acknowledged people's right to protest within the framework of the law but warned protesters against attempting to undermine the country's security.

"Under any circumstances, the country's security and the people's calm are the top priority for the law enforcement and our security and military forces," Rahmani Fazli is reported to have said.

Iranian protesters gather around a burning car Saturday in the capital city of Tehran.

'The decision must be implemented'

Supreme Leader Khamenei said Sunday he supported the government's decision to raise gas prices, Press TV reported, but urged officials not to increase the price of other commodities.

"If the heads of the three branches of the government make a decision [about it], I will support," Khamenei is reported to have said. "The decision must be implemented."

According to Reuters, state television reported that Khamenei blamed opponents and foreign enemies for "sabotage," saying: "The counter-revolution and Iran's enemies have always supported sabotage and breaches of security and continue to do so."

The White House released a statement on Sunday supporting "the Iranian people in their peaceful protests against the regime that is supposed to lead them."

"We condemn the lethal force and severe communications restrictions used against demonstrators. Tehran has fanatically pursued nuclear weapons and missile programs, and supported terrorism, turning a proud nation into another cautionary tale of what happens when a ruling class abandons its people and embarks on a crusade for personal power and riches," the statement reads.

Internet service shut down

The price hike reflects an increase ranging from 50% to 300%.

The price of a gallon of regular gas jumped to 57,000 rials from 40,000 rials per gallon, while the monthly subsidized ration for each private car has been reduced from 70 gallons to 16 gallons, after which the price of gas rises to 114,000 rials per gallon.

At official exchange rates, 57,000 rials is worth $1.71, and 114,000 rials is $3.42; however the official market exchange is not representative of the real value of the currency -- the open market is. This means that the typical price of a gallon of gas now costs anywhere from 50 cents to about $1.

Escalating inflation and an IMF forecast of slow growth could make driving unaffordable for middle class families. According to UN estimates in 2017 the median salary in Iran is $3,300 a year.

Demonstrators gather Saturday in Tehran.

Iran, which is a founding member of the Organization of the Petroleum Exporting Countries (OPEC), currently has estimated proven crude oil reserves of 155.6 billion barrels, according to energy giant BP.

Earlier this month President Hassan Rouhani announced the discovery of a vast oil field containing an estimated 53 billion barrels of crude oil, which would make it Iran's second-largest oil field.

The government says the increase is in the interest of the country and argues it will prevent "fuel smugglers" from exporting Iran's oil to neighboring countries.

However, analysts and opposition figures say the main problem is a weak economy, with the country undergoing deep economic difficulties marked by rising inflation, growing unemployment, corruption and pressure from US sanctions.

Over the weekend, the hashtag #300% went viral, according to social media users and reporters in Iran. That was soon followed by a near-total internet shutdown. It's unclear if these events are related.

Iran's nationwide internet and cell phone shutdown passed the 24-hour mark, the longest such outage since at least 2013.

Researchers at Netblocks, a group that tracks global connectivity, first noticed major drops in connectivity in Tehran and other cities Friday afternoon. Iran has instituted partial or full internet blocks plenty of times in the past, but rarely at this scale.

Nearly two years ago, unrest over poor living standards led to some calling on Shi'ite Muslim clerical leaders to step down. Iranian officials said 22 people died in those protests.

Clarification: This story has been updated to more accurately reflect the current price of a gallon of gas in Iran.