As the coronavirus started surging in New Jersey’s largest city, officials introduced the state’s first new coronavirus lockdown two weeks ago, mandating an 8 p.m. indoor closing time for all restaurants, bars and nonessential businesses citywide.

But then the number of new cases in the city, Newark, climbed even higher: Over the last four days, there have been 842 new reported infections, and 19 percent of people tested over three days last week were found to have the virus, city and county officials said.

The uptick mirrors a troubling statewide trend that has resulted in a spike in Covid-19 hospitalizations across New Jersey to levels not seen since June.

On Tuesday, New Jersey reported 3,877 new cases, a figure the governor called “devastating.” By the next day, 3,078 new cases were recorded. Hospitals also reported 15 coronavirus deaths, adding to the more than 16,400 New Jersey fatalities already linked to the virus.

Newark, a commuter hub, is about a 15-mile drive from New York City, where officials are struggling to contain an outbreak on Staten Island and bracing for a second wave of cases citywide.

New York’s governor has announced that bars, restaurants and gyms across the state must close nightly at 10 p.m. starting Friday, and that private residential gatherings should not exceed 10 people.

Of the Northeast states, only Rhode Island and Connecticut have higher rates of infection per 100,000 residents than New Jersey, according to a New York Times database.

The rates in Massachusetts and Pennsylvania are not far behind, however, as the region, which had been an early epicenter of the pandemic, struggles to regain control of a virus that had largely been tamped down just a few months ago.

Alarmed by the new data, Newark turned to a new tactic on Tuesday.

The mayor, Ras J. Baraka, implemented a sweeping set of rules designed to avoid a repeat of the springtime outbreak of the coronavirus, which has been linked to at least 680 deaths in the city of 282,000 — the hardest-hit municipality in the state’s hardest-hit county, Essex.

Mr. Baraka, a Democrat, ordered a 9 p.m. weekday curfew for residents of three ZIP codes and the cancellation of all team sports activities citywide, effective immediately. Newark’s nursing homes were barred from accepting visitors for two weeks. And gatherings throughout the city — indoors and outdoors — were capped at 10 people until at least Dec. 1.

Aides said Mr. Baraka would not hesitate to shut down businesses, issue fines and suspend liquor licenses.

The tough talk has created an inherent tension between Gov. Philip D. Murphy, a Democrat, and Mr. Baraka, one of his closest political allies.

Mr. Murphy had taken pains to say that he had no desire to renew a statewide lockdown as he announced limited measures that kick in on Thursday: 10 p.m. indoor closing times at nightclubs and restaurants; no seating at bars; and a ban on out-of-state youth sports tournaments.

One in five residents of Newark tested positive for the virus last week. Credit...Bryan Anselm for The New York Times

But when asked about Newark’s rules, Mr. Murphy’s top lawyer, Parimal Garg, said that state law superseded actions taken by municipalities. Mr. Murphy’s aides declined to comment on Tuesday or Wednesday about the confusion.

“Newark’s prescription is not the state’s prescription,” Mr. Baraka said in a statement on Tuesday. “Stricter measures are required in the city’s hot spots in order to contain the virus and limit the spread. I know we are all tired, but the virus is not.”

On Tuesday night in Newark, less than an hour before the curfew took hold, Daysi Moreno, a hairdresser, rushed to pull down the gates to the store she owns on Bloomfield Avenue, a bustling business corridor in the city’s North Ward.

Six blocks away, in Branch Brook Park, a club softball team for girls was practicing, preparing to leave in the coming days for a tournament in Clearwater, Fla.

“We kept waiting for the lights to shut off, but they didn’t — so we kept practicing,” said Jessie Dreswick, 24, one of the coaches for the team, the New Jersey Pride. “I’m just happy we’re still playing.”

Based on the guidance from the city and state, the team should not have been on the field or preparing to travel out of state. But the competing shutdown orders were adding to a sense of trepidation in New Jersey.

“There is confusion,” said Perry N. Halkitis, a dean of biostatistics and urban-global public health at the School of Public Health at Rutgers University. “Mixed messaging.”

But he said the governor’s overarching approach, and the emphasis on quelling indoor drinking during late-night hours, when inhibitions drop, was appropriate. He said he was equally concerned about private indoor gatherings that are harder to monitor.

“People feel like it’s their God-given right to be with their families on Thanksgiving,” said Dr. Halkitis, who lives and works in Newark.

“You really love your family?” he added. “For Thanksgiving, you should not be with them.”

The governor has repeatedly said that private indoor gatherings are a main source of spread. Halloween parties were linked to five outbreaks across the state, involving a total of 70 people, state health officials said on Wednesday.

Edward Lifshitz, medical director for the Communicable Disease Service at New Jersey’s Department of Health, said that it was often hard to pinpoint a precise source of infection, given the limits of contact tracing and people’s travel habits.

What is clear is that the virus is now spreading rapidly through the community, and that indoor gatherings remain less safe than outdoor events, he said. Elementary and middle schools have not been shown to be a major source of spread, Dr. Lifshitz said; K-12 schools are linked to 146 cases since the start of September.

The seven-day average rate of positive virus tests in New Jersey was 7.95 percent.

“We need to separate as much as possible,” Dr. Lifshitz said. “It’s hard wearing that mask every day. It’s hard not being able to see your friends and family. But none of them are as hard as dealing with the loss of a family member or a friend.”

In Newark, Ms. Moreno, 47, said she had cut the number of staffers at Latinos Beauty Salon to six people, down from 10, after salons in the city were told late last month they could remain open for appointments only.

She said she would prefer a total lockdown for the month of January, to give the state a chance to recover for good. “Business is very slow now,” she said. “Appointment-only is hard for people figuring out when they come off work.”

Residents of three Newark ZIP codes — 07104, 07105 and 07107 — are being asked to remain off the street after 9 p.m. on weekdays and 10 p.m. on weekends, until 5 a.m., unless traveling to or from work, or in the case of an emergency.

The weather during the first night of the curfew was balmy, but the streets were like ghost towns.

Still, the ovens at Calandra’s Bakery on First Avenue, in a section of Newark now subject to the mandatory curfew, remained on, operating 24 hours a day to supply supermarkets from New York City to Pennsylvania with handmade bread.

A Calandra’s manager, Carlos Ribeiro, 55, said his hands were chapped from constant washing.

“If I touch something, I wash. I support masks 200 percent!” Mr. Ribeiro said. “Everybody worries. We are concerned. It’s why we are more and more on top of the employees: ‘Wash your hands, keep your distance.’

“We all need to help each other.”