SYDNEY — Australia’s biggest city, Sydney, extended a lockdown by four weeks on Wednesday after an already protracted stay-at-home order failed to douse a coronavirus disease 2019 (COVID-19) outbreak, with authorities warning of tougher policing to stamp out non-compliance.  

Far from a planned exit from lockdown in three days, the city of 5 million people and neighboring regional centers spanning 200 km (120 miles) of coastline were told to stay home until Aug. 28 following persistently high case numbers since a flare-up of the virulent Delta variant began last month.  

The state of New South Wales (NSW), of which Sydney is the capital, reported 177 new cases for Tuesday, from 172 on Monday. That is the biggest increase since an unmasked, unvaccinated airport driver was said to have sparked the current outbreak. The state also reported the death of a woman in her 90s, the 11th death of the outbreak.  

Of particular concern, at least 46 of the new cases were people active in the community before being diagnosed, raising the likelihood of transmission, said authorities. They have cautioned that active community transmission must be near zero before rules are relaxed.  

“I am as upset and frustrated as all of you that we were not able to get the case numbers we would have liked at this point in time but that is the reality,” state Premier Gladys Berejiklian told a televised news conference.  

Ms. Berejiklian added police would boost enforcement of wide-ranging social distancing rules and urged people to report suspected wrongdoing, saying “we cannot put up with people continuing to do the wrong thing because it is setting us all back.” 

In one case, a mourning ceremony attended by 50 people in violation of lockdown rules resulted in 45 infections, she said.  

The extension turns what was initially intended to be a “snap” lockdown of Australia’s most populous city into one of the country’s longest since the start of the pandemic, and may spark the second recession of the $1.47 trillion national economy in two years, according to economists.  

To minimize the economic impact, the NSW government said it would lift a ban on non-occupied construction in most of Sydney. However, it expanded a list of local government areas within the city where the ban would stay because of the prevalence of COVID-19 cases there.  

“It’s getting really difficult, day in and out, day by day, for us to continue running the same business,” said Raihan Ahmed, a convenience store owner at Bankstown, one of the main affected suburbs. “Somehow we have to survive, and we are trying our best.”  

Opinion polls have shown slipping support for Prime Minister Scott Morrison’s government amid criticism of a slow vaccination roll-out that has been blamed on changing regulatory advice and supply shortages.  

“There is no other shortcut, there is no other way through, we have to just hunker down and push through,” Mr. Morrison said during a televised news conference in the national capital Canberra.  

All Australians who wanted a vaccination would receive it by the end of the year, and “I would expect by Christmas that we would be seeing a very different Australia to what we are seeing now,” he added.  

The NSW government said it was redirecting Pfizer Inc vaccine doses, which have so far been restricted to people aged 40–60, from relatively unaffected regional areas to final-year school students in the worst-affected Sydney neighborhoods.  

The state and federal governments also said they were expanding relief funding to enable affected companies to keep paying wages through the closure.  

In contrast to New South Wales, the states of Victoria and South Australia began their first day out of shorter lockdowns that halted outbreaks there. Victoria reported eight new cases, all of them isolated throughout their infectious period, and another case still under investigation.  

Australia has kept its COVID-19 numbers relatively low, with just over 33,200 cases and 921 deaths, out of a population of about 25 million, since the pandemic began. — Renju Jose and Byron Kaye/Reuters