MELBOURNE, Australia — A new wave of coronavirus infections prompted officials to impose restrictions on some 5 million people in Australia's second-largest city, illustrating the difficulty of conquering the pandemic even in a country that had enjoyed relative success in taming its toll.

Authorities in Melbourne, the capital of Victoria state, said they would reinstate curbs for six weeks starting Wednesday night to try to beat back a surge in new cases that threatens to spiral out of control.

The resurgence of the virus in Melbourne echoes the difficulties facing the United States, where some areas, particularly in the South and West, are mandating masks and reimposing shutdowns as they report spiraling numbers of infections and hospitalizations.

Still, with a total of 8,755 cases and 106 deaths among a population of 25 million, Australia has largely avoided the devastating effects seen in many other Western countries.

The United States has a population 13 times that of Australia but has recorded more than 1,200 times the number of deaths.

New South Wales, the most populous state, on Tuesday reported only seven new cases, while three states and two territories recorded none.

Bennett said the state had not been sufficiently prepared to shield high-risk vulnerable populations like the residents of the housing towers under hard lockdown, many of whom are new migrants, refugees, those with mental health issues and survivors of family violence.

Ahmed Dini, a resident of one of the towers, said Tuesday that residents felt they had been treated like second-class citizens, yet on the other hand they had received an outpouring of public support.