SYDNEY (AFP) - Sydney's five million residents will be in Covid-19 lockdown for at least another two weeks, state premier Gladys Berejiklian announced on Wednesday (July 14), rejecting calls to tighten restrictions further.

Australia's largest city is already in its third week of a partial lockdown and struggling to bring a fast-spreading outbreak of the coronavirus Delta variant under control.

In the past 24 hours, 97 new cases were recorded, more than the 89 reported the previous day.

Australia had been widely lauded for its early handling of the pandemic.

But a painfully slow vaccine roll-out has left less than 10 per cent of the population protected as much of the world gingerly reopens.

"It always hurts to say this, but we need to extend the lockdown, at least a further two weeks," said Ms Berejiklian, premier of New South Wales state, of which Sydney is the capital.

Under Australia's "Covid zero" strategy, the authorities are trying to stamp out community transmission completely.

Sydney's lockdown was due to end on Friday, but that date has now been pushed back until July 30.

"I appreciate people are stressed and upset about what is going on, myself included," Ms Berejiklian said. "None of us want to be in this situation. But it is our job to keep the community safe."

Most Sydney residents are allowed to leave home for exercise, essential shopping, work or health reasons, but schools are closed and people are encouraged to remain at home.

The authorities have rejected calls for the lockdown to be more stringent, with critics pointing out that "essential work" rules allow stores such as Ikea and Louis Vuitton to remain open.

"I appreciate there are a lot of opinions out there, but please know every decision we take is based on that expert health advice," said Ms Berejiklian.

'Send Beer'

Some hot spot areas are subject to tighter restrictions, including a Bondi apartment block that was fully locked down after nine cases were detected.

On Tuesday, the police guarded the front and rear of the building to prevent residents from leaving. A sign taped to one apartment window read "Send Beer".

Ms Berejiklian did not rule out more stringent citywide restrictions if cases continued to rise.

Australia's latest Covid-19 outbreak began in the middle of last month and has since grown to 864 cases.

Twenty people are in intensive care and two have died.

The outbreak is believed to have begun with an unvaccinated driver who had been working with international air crews.

Sydney is virtually cut off from the rest of the country, with residents banned from entering many states and cities.

Australia's international borders have been mostly sealed since March 2020, and are not expected to open before the end of the year.

Since the pandemic began, Australia has recorded more than 31,000 virus cases and 912 deaths in a population of 25 million.