SYDNEY (BLOOMBERG) - Sydney's delta-variant coronavirus outbreak is proving difficult to bring under control, despite Australia's most-populous city being in lockdown for almost a week.

The city of almost 6 million people detected 24 new locally acquired cases in the past 24 hours, New South Wales state Premier Gladys Berejiklian told reporters on Thursday (July 1).

Since the outbreak began in mid-June from a driver who transported international flight crew, Sydney has recorded 195 infections.

Half of the new cases announced Thursday were from people in the community while infectious, creating "a cause of concern," Berejiklian said. "In too many examples we are seeing workers who are leaving the house with symptoms or going to work," she added.

The outbreak in Sydney is at the centre of new coronavirus infections that have placed about half of Australia's population of 25 million people into lockdown. While health authorities are racing to stamp out continent-wide outbreaks of the delta variant, South Australia state on Thursday announced that it had recorded no new cases.

In stark contrast to freedoms enjoyed by Australians just months ago, stay-at-home and mandatory mask-wearing orders have been imposed in major cities such as Sydney, Brisbane and Perth. On Wednesday, they were joined by the remote Outback town of Alice Springs - close to the natural tourist attraction of Uluru and home to thousands of vulnerable indigenous peoples.

The outbreaks are ramping up pressure on Prime Minister Scott Morrison to increase the pace of a tardy vaccine roll-out, which has been hit by supply-chain hold-ups. The Bloomberg Vaccine Tracker shows the nation is ahead of only near neighbor New Zealand among the 38 OECD nations in administering doses.

In an interview on Bloomberg Television interview on Thursday, Queensland state Treasurer Cameron Dick said Morrison's government should have secured more contracts from drug-makers, with the nation currently limited to the AstraZeneca and Pfizer products.

"Other jurisdictions effectively spread the risk across a whole range of vaccines - that was the case in the US and the UK," Dick said. "All the states and territories are in the hands of our federal government. They are the ones securing supplies of our vaccines."