ISTANBUL — Iran’s supreme leader on Sunday endorsed a government decision to cut fuel subsidies and warned demonstrators against clashing with security forces, raising fears of a crackdown as the economy falters under U.S. sanctions.

In a televised address, Ayatollah Ali Khamenei said he supports the measure to push up gasoline prices and ration supplies, a move designed to raise funds for cash handouts to the poor.

The abrupt decision, announced Friday, sparked demonstrations in about two dozen locations across the country as residents already grappling with soaring inflation called on the government to reverse the hike.

In towns and cities across Iran, drivers abandoned vehicles on highways and protesters blocked roads and set tires and buildings alight. Some demonstrators clashed with baton-wielding security forces, officials said, and at least one protester and a police officer were killed.

Sporadic demonstrations continued in multiple cities Sunday, according to residents and videos posted on social media. A demonstrator in the capital reached by phone said protesters continued to confront police on the streets of central Tehran. Other protests were reported in Shiraz, Tabriz, Kermanshah and Sanandaj.

In the northeastern city of Mashhad, the streets were deserted early Sunday, one resident said. Reached by telephone, he said some businesses had closed to protest the cut to fuel subsidies. Both residents spoke on the condition of anonymity because of fears of reprisals from security forces.

 In Isfahan in central Iran, merchants in the bazaar shuttered their shops, according to a video posted by the BBC Persian service. Also Sunday, the government ordered a blanket restriction on Internet access nationwide, local news agencies reported, quoting an anonymous source in the Information and Communications Technology Ministry.

“Access to the Internet has been limited since last night,” the source said, according to the semiofficial Iranian Students’ News Agency.

“Iran is in the midst of a near-total national Internet shutdown,” the civil society group NetBlocks, which monitors Internet access worldwide, said in a statement.

 Parliament held an emergency session Sunday to address the crisis, the state-run Islamic Republic News Agency reported. The protests underscored the difficulties that Iran’s rulers face as they try to blunt the effects of harsh U.S. sanctions while containing the frustration of many Iranians fed up with rising prices and a system they say is incapable of reform.

Iran’s currency has plummeted in recent years, and Iranians have watched their budgets shrink and savings evaporate amid widespread corruption and government waste. Similar changes to government subsidies set off a wave of unrest in December 2017, when more than two dozen people were killed in protests nationwide.

The decree Friday followed a meeting of Iran’s Supreme Economic Coordination Council, which is presided by President Hassan Rouhani and includes judiciary chief Ebrahim Raisi and the speaker of parliament, Ali Larijani.

The council raised the cost of gasoline 50 percent, up to a minimum of 15,000 rials (13 cents) per liter, or about 50 cents per gallon. Under the measure, consumers can purchase up to 60 liters at the minimum price, after which they will be charged 30,000 rials per liter. Previously, consumers could buy as many as 250 liters at the subsidized price.

Rouhani defended the decision at a cabinet meeting Sunday, local media reported.

“The government’s goal . . . is to help the middle class and lower-income households,” he said, according to the Mehr news agency.

He said the government had only three options to reach this goal.

“We must either increase taxes, export more oil or decrease subsidies and return them back to those in need,” Mehr quoted Rouhani as saying. 

 Khamenei, in his address, said he understood the concerns among ordinary Iranians that the price hike would raise the costs of other goods.

Government officials “should be careful about this. They should take appropriate measures to prevent inflation,” he said, according to an official transcript of his remarks.

Still, he said the decision “should be enforced” and called on citizens to “separate themselves” from those he identified as “thugs” seeking to exploit the chaos.

“This is my advice,” he said. “They should realize who is responsible for the burning, breaking, sabotage, fights and insecurity.”

The demonstrations came amid heightened tensions with the United States, which has sought to pressure Iran to negotiate an end to its nuclear energy and ballistic missile programs. The campaign includes a near-total trade embargo on the Iranian economy, including restrictions on financial transactions, oil exports and other major industries.

Iran is home to the fourth-largest crude oil reserves in the world and has some of the most heavily subsidized gas prices.

“Like most energy producers, the Iranian state has basically subsidized the living standard of its citizens for decades,” said Esfandyar Batmanghelidj, founder of Bourse & Bazaar, a website that features economic analysis on Iran. “It is a really inefficient means to support the welfare of ordinary Iranians; cash transfers are much better.”

The lack of a robust debate over the new policy, however, set the stage for the outburst of protests, analysts said.

“There is no question that it was high time that the gasoline subsidy was eliminated,” Djavad Salehi-Isfahani, an economics professor at Virginia Tech, wrote Sunday in a post on his blog on the Iranian economy.

But “for a distressed and incredulous public, government promises to pay are not the same as money in the bank,” he continued.

A spokesman for Iranian police said Sunday that they would confront anyone attempting to undermine “public order.”

“Some individuals who are led by enemies outside the country are taking advantage of people’s demands to undermine public security and order,” Brig. Gen. Ahmad Noorjan said, according to Mehr.

Iran’s Intelligence Ministry issued a statement saying it had identified those “playing a key role in igniting the unrest.”

“Measures are being taken and the results will be announced soon,” the statement said.