Coronavirus Live Updates: U.S. Sets New Single-Day Case Record

The Iranian government, already struggling under the weight of international sanctions, has been especially reluctant to lock down. Its president once said the economy must remain open because Iran “did not have a second option.”

But on Wednesday, as infections surged, hospitals filled and the death toll climbed, Iranian officials announced new shutdown measures in cities across 11 provinces.

Health ministry officials said eight provinces, including Tehran, the capital, were now considered red zones.

Dr. Alireza Zali, head of Tehran’s virus management committee, told local news media that he had requested a partial shutdown for Tehran that would limit movement, cut back work hours and ban large gatherings like weddings and funerals.

And wearing a mask in public spaces will be mandatory as of next week.

“It’s because of a change in numbers in the past week for people infected, hospitalized and death rates,” Dr. Zali said. Tehran, he reported, has had a nearly 8 percent increase in hospitalization in the past 24 hours.

In April, Iran shut down for several weeks. But the next month, worried about the economy, it lifted restrictions, even though the country had not met any of the benchmarks health experts set out for reopenings, among them a steady decline in the number of new infections or contact and tracing measures.

As the country reopened, many Iranians abandoned measures like wearing masks and social distancing and essentially resumed ordinary life. But cases began to spike after about a month — and they have been steadily increasing since. On average, said the deputy health minister, Iraj Harirchi, one Iranian dies every 10 minutes from Covid-19, and every 35 seconds one contracts the virus.