ISTANBUL — A dramatic surge in coronavirus infections in Iran has rekindled the largest outbreak in the Middle East, just weeks after the country appeared to have tamed its epidemic.

Iran is again reporting an average of more than 3,000 new cases each day and on Thursday recorded its largest single-day total, more than 3,500 new infections, raising the total to about 164,000, the official IRNA news agency said.

While the epidemic was initially concentrated in the capital, Tehran, and the holy city of Qom, the new flare-up has largely been centered in Khuzestan province, an oil-rich region in Iran’s southwest.

There, an ethnic Arab minority, which has long complained of discrimination, has at times balked at central government control. Doctors and residents say that widespread disregard for public health restrictions in Khuzestan has helped fuel the pathogen’s spread.

“The numbers are really high now. Most people can’t find masks, and no one has been taking social distancing seriously,” said a pediatrician at the Nezam Mafi hospital in the city of Dezful, one of the centers of Khuzestan’s outbreak. She spoke on the condition of anonymity to more freely discuss conditions in the area.

In her hospital alone, she said, at least 40 staff members tested positive for the virus, and the intensive care unit was shuttered as a result.

A relative lack of infrastructure has undercut efforts to address the public health emergency in the province. Clinics and hospitals are overwhelmed, the local economy has ground to a halt and a water shortage near the provincial capital, Ahvaz, has driven angry residents into the streets.

“How can I take a shower or even just wash my hands if I don’t have any water? We haven’t had water for a whole month,” a resident of Ahvaz yelled angrily in a video recently posted on social media. He is flanked by several other men, some of whom are wearing masks and shouting in agreement.

Two weeks ago, residents of Gheyzanieh, a farming hamlet near Ahvaz, protested the lack of potable water and were fired at by security forces. “If I want to defend my rights, they [the government] respond to me with bullets,” the man said. “It doesn’t matter anymore, I want to die. . . . Death is better than this life.”

Khuzestan, an arid expanse on Iraq’s border, is home to the majority of Iran’s oil and gas reserves and is vital to trade both overland and through ports on the Persian Gulf. Any prolonged outbreak there could pose a challenge to Iran’s government, which relies on its wealth and industry and is already accused by the local population of ignoring its many grievances.

During nationwide protests late last year sparked by fuel price hikes, the worst violence was in Khuzestan, where security forces in Mahshahr city responded to roadblocks erected by demonstrators by opening fire with heavy weapons, according to human rights groups. At least a dozen people were killed, with some estimates putting the toll much higher.

“Khuzestan is definitely of strategic significance to Iran,” said Alex Vatanka, director of the Iran Program at the Middle East Institute in Washington. He added, “There are a couple of interesting factors that create a sensitive cocktail.”

Iran was one of the first countries to see a major outbreak of the coronavirus after it emerged in China. Since February, the virus has killed more than 8,000 Iranians and sickened another 164,000, according to official reports that health experts say underestimate the true magnitude of the toll.

Earlier in the epidemic, the government enacted, at times, haphazard restrictions. These were often ignored by ordinary Iranians, who continued to travel, shop, visit their families and, in some cases, work. But after the outbreak peaked in early April, the epidemic seemed to slow, and most curbs on economic and social life were lifted by the middle of that month.

Some Iranian analysts and health officials have been quoted in the country’s media blaming the loosening of restrictions for the new spike in infections. Iranian government officials, for their part, have faulted the population, including in Khuzestan, for flouting public health measures, such as bans on large gatherings and long-distance travel.

Iranian President Hassan Rouhani said Wednesday that stricter restrictions may have to be reimposed if the public does not adhere to the more relaxed guidelines.

“The reemergence of coronavirus, beyond any economic damage, will threaten the health of our dear people and it is not appropriate now that the achievements be lost due to negligence,” Rouhani said in remarks published on his website.

Khuzestan’s infections now account for about a quarter of Iran’s total daily cases, according to figures released by health officials. Nearly 600 people have already died in the province of the virus and more than 13,000 have fallen ill, according to Ali Ehsanpour, spokesman for Ahwaz’s Jondi Shapour University of Medical Sciences. Local doctors say the official tally is probably an ­undercount.

“Based on what I’ve seen, there are a lot of undiagnosed patients circulating within the society and spreading the disease,” said Mohammadreza, a medical resident at Jondi Shapour University. He spoke on the condition that his full name not be used so he could comment freely about the spread of the virus.

“And with the increase in the number of patients and our lack of space at the hospitals, many are being sent home to self-quarantine,” he said. “But they are not taking the warnings seriously and continue to engage in high-risk behavior.”

In Dezful, a city of more than 400,000 residents, an increase in coronavirus testing has revealed the extent of what may be the province’s worst outbreak. According to the head of the local medical university, Yousef Paridar, quoted by Iranian media late last month, a staggering 37 percent of people tested were positive for the virus.

The pediatrician in Dezful said few government institutions appear to be capable of addressing the contagion and that Khuzestan’s poverty and poor infrastructure have made the fight against the virus an uphill battle.

A cash shortage in the local economy has taken a toll on Khuzestan’s emergency responders. Dozens of medical workers in Dezful staged walkouts late last month to protest late wage payments. A senior official of the Health Ministry, Maryam Hazrati, said this month that she was seeking to send more nurses to Khuzestan from other provinces.

“We are trying to . . . prevent medical teams from burning out in these difficult conditions,” she said, according to IRNA.

Even before the new waves of cases, the epidemic was causing economic pain in Khuzestan, threatening to make living conditions far worse for many residents. IRNA quoted an ­Ahwaz-based economics professor saying that at least 160 companies have been negatively affected and that tens of thousands of workers either temporarily or permanently lost their jobs.

Adam Taylor in Washington contributed to this report.