Australia's New South Wales has logged its second-highest daily increase of the year in locally acquired Covid-19 cases, amid fears of a wave of new infections after thousands of people joined an anti-lockdown protest.

"In relation to yesterday's protests, can I say how absolutely disgusted I was. It broke my heart," Gladys Berejiklian, the premier of the country's most populous state, told the media.

"I hope it won't be a setback, but it could be," she said.

There were 141 Covid-19 cases reported, down from 163 a day earlier.

The outbreak, which began in June, is being driven by the highly contagious Delta variant of the virus, and has now infected 2,081 people in New South Wales.

There are 43 people in intensive care, up from 37 a day earlier.

Gladys Berejiklian takes questions during a Covid-19 update and press conference

Under fire for a slow vaccine roll-out, Australian Prime Minister Scott Morrison said more vaccine supply was not going to ensure New South Wales gets out of lockdown, but what was needed was an effective, properly enforced lockdown.

"Let me be clear - there's not an alternative to the lockdown in New South Wales to get this under control.

There is no other magic bullet that's going to do that," Mr Morrison said during a televised media conference.

Prime Minister Scott Morrison says lockdown is not optional

He called the anti-lockdown protests in Sydney reckless and self-defeating.

While Ms Berejiklian and other state leaders have blamed Canberra for the slow vaccine roll-out, critics have said NSW did not enforce its stay-at-home orders, which has led to Delta variant leaks to other states.

At least 38 of the new cases in NSW had spent time in the community while infectious, state health authorities said.

Numbers of such cases have stayed stubbornly high even after four weeks of lockdown in Sydney, now expected to be extended beyond 30 July.

The state reported two deaths overnight, including a woman in her 30s with no pre-existing conditions.

Despite its struggle with spikes of infections, Australia has managed to keep its epidemic largely under control with a total of about 32,600 cases and 918 deaths.

To help speed up vaccinations in Sydney, the government's official adviser, the Australian Technical Advisory Group on Immunisation, on Saturday changed its advice on the AstraZeneca vaccine, urging anyone in the city under the age of 60 to strongly consider getting vaccinated with it.

A man receives a Covid-19 vaccine inside the Melbourne Showgrounds vaccination centre

ATAGI had previously advised against the AstraZeneca vaccine for people under 60 due to concerns about blood clots.

"In the context of the current risk of Covid-19 in NSW and with the ongoing constraints on Comirnaty (Pfizer) vaccine supplies, all adults in greater Sydney should strongly consider the benefits of earlier protection with Covid-19 Vaccine AstraZeneca rather than waiting for alternative vaccines," ATAGI said in a statement.

Mr Morrison has said the government has secured an additional 85 million doses of the Pfizer vaccine, but they will only be delivered in 2022 and 2023.

"To have those booster shots pre-ordered means we can go into 2022 with confidence," he said.

Australia's Victoria state reported 11 locally acquired COVID-19 cases on Sunday, down from 12 a day earlier, raising hopes the state will end a hard lockdown imposed 10 days ago.

State Premier Daniel Andrews said it was too early to say whether restrictions will be eased on Tuesday, but: "At this stage, though, things are going well."

All of the cases were linked to the current outbreak clusters and all of them were in isolation throughout their infectious period, the state's health department said.

South Australia reported three new cases on Sunday.

Thousands take part in 'Freedom' protests

Vietnam says more US vaccine donations expected after first 5 mln doses

The US is considering giving more Coronavirus vaccines to Vietnam, its ambassador to the United States said on Sunday, as the Southeast Asian country struggles to control outbreaks of the fast-spreading Delta variant of the virus.

After successfully containing the virus for much of the pandemic, Vietnam has been facing rapid outbreaks of infections, with daily cases repeatedly hitting new highs.

Vietnam took delivery of a shipment of 3 million Moderna doses from the United States on Sunday, taking the amount given by the United States, via the global Covax vaccine scheme, to five million doses.

"The US side has said it is also considering more vaccine donations to Vietnam soon," the ambassador to the United States, Ha Kim Ngoc, said speech posted on a government web site.

Vietnam is also in talks with the United States on domestic production of mRNA vaccines, its foreign ministry said on Thursday, adding that production could begin in the fourth quarter or early in 2022.

The ministry did not identify the US and Vietnamese companies involved in the talks.

State media reported on Saturday Vietnamese conglomerate Vingroup was in talks with San Diego-headquartered Arcturus Therapeutics Holding on mRNA vaccine production.

Clinical trials could begin in Vietnam in August, the Tuoi Tre newspaper reported, adding that the firms could produce 100 million to 200 million doses a year under such a deal.

Vingroup and Arcturus did not immediately respond to requests for comment.

Vietnam kept the virus at bay for the first year of the pandemic but infections have been spreading quickly since late April.

The health ministry reported 7,968 infections on Saturday, a record daily increase.

In all, it has recorded nearly 95,000 infections and at least 370 deaths, most in the southern commercial hub of Ho Chi Minh City.

Nearly half of the latest shipment of Moderna vaccines will be sent to that city, the U.S. Embassy in Hanoi said on Saturday.

China reports 32 new Covid-19 cases vs 35 a day earlier

China reported 32 new Covid-19 cases in the mainland on July 24, down from 35 cases a day earlier, the national health authority said.

The National Health Commission said in a statement five of the new cases were local infections, down from 13 the day before. Two were in the eastern province of Jiangsu, and there was one each in Liaoning, Yunnan and Guangdong provinces.

The number of new asymptomatic cases, which China does not classify as confirmed cases, fell to 17 from 20 the day before.

The total number of confirmed Covid-19 cases in mainland China stands at 92,529, while the death toll unchanged at 4,636.