New Zealand's government has reported that new Covid-19 cases fell for a second day, down to 49, amid the tight lockdown the country undertook during the latest outbreak this month.

Except for a small number of cases in February, New Zealand was mainly coronavirus-free for months, until an outbreak of the Delta variant imported from Australia prompted Prime Minister Jacinda Ardern to order a snap nationwide lockdown on 17 August.

The total number of cases in the outbreak is at 612, with 597 in New Zealand's largest city of Auckland and 15 in the capital Wellington.

The declining number of daily cases signals that the social restrictions are reducing the spread of the Delta variant, Ms Ardern said in a news conference.

"We have a second day where our numbers have declined. We want the tail of this outbreak to be as short as possible," Ms Ardern said.

Around 1.7 million Aucklanders will remain in strict level 4 lockdown for another two weeks, while restrictions for the remainder of the country will ease slightly from tomorrow.

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Police placed checkpoints at the outskirts of Auckland to ensure no non-essential movement was allowed into the city.

Police also said they had arrested 19 people today following anti-lockdown protests around the country.

There are now 33 people in hospitals from the latest Delta outbreak, the Director General of Health Dr Ashley Bloomfield said, with eight cases in stable condition in intensive care.

"It is sobering to see six cases in the outbreak are under the age of one," he said.

But he added that the public health measures in place were slowing the spread of the virus and cases will continue to decline.

Lockdowns, along with closing the international border from March 2020, were credited with reining in Covid-19.

However, the government now faces questions over a delayed vaccine rollout, as well as rising costs in a country heavily reliant on an immigrant workforce.

Just over a quarter of the population has been fully vaccinated so far, the slowest pace among the wealthy nations of the OECD grouping.

Australia in vaccine swap pact with Singapore as COVID-19 cases surge

Australia will receive 500,000 doses of Pfizer's Covid-19 vaccine from Singapore this week, Prime Minister Scott Morrison said, after the government agreed a swap deal in a bid to curtail surging coronavirus infections.

The agreement, which will see Australia return the same amount of Pfizer vaccine doses to Singapore in December, will allow Canberra to accelerate its vaccination programme as daily cases near record levels for the country.

"That means there are 500,000 doses extra that will happen in September that otherwise would have had to wait for several months from now, accelerating our vaccination program at this critical time as we walk towards those 70% and 80% targets," Mr Morrison told reporters in Canberra.

A man jogs past a Covid-19 mural on Bondi Beach, Sydney

While Australia had managed to successfully contain the coronavirus with a system of strict lockdowns and quarantine, a slow vaccination rollout has made the country vulnerable to the highly infectious Delta variant.

With just under 28% of Australia's population fully vaccinated, compared with 80% in Singapore, several states and territories have had to implement strict lockdowns as cases soared, hitting businesses and the domestic economy.

Capital city Canberra today extended its hard lockdown by a further two weeks, and Victoria, the country's second most populous state, is expected to soon follow suit.

Canberra has been in lockdown for three weeks after a spate of cases believed to have spread from New South Wales, the epicentre of Australia's Covid-19 outbreak.

"We are bending the curve down and are getting on top of the outbreak. However, it is a slow process and it will take more time," Australian Capital Territory Chief Minister Andrew Barr told reporters in Canberra.

Canberra reported 13 new cases in the past 24hours. New South Wales reported 1,164 new infections, down slightly from a record 1,290 cases the day prior.

Victoria, which has been in lockdown for five weeks, reported 76 new locally acquired coronavirus cases in the past 24 hours, up marginally from 73 cases reported the previous day.

People in Melbourne walk past a sign encouraging people to get vaccinated

State Premier Dan Andrews said too many people remain unvaccinated to significantly ease restrictions, but that Victoria would outline a plan tomorrow to reduce curbs as vaccination levels rise.

Australia has recorded nearly 54,000 Covid-19 cases and 1,006 deaths since the start of the pandemic, still lower than the caseload and death toll in most comparable nations.