More than two million people in Brisbane entered a three-day lockdown Monday after a cluster of coronavirus cases was detected in Australia's third-biggest city.

It is the second snap lockdown of the greater Brisbane area this year, and comes after seven people tested positive for Covid-19 -- the first significant community outbreak in Australia in weeks.

"This is the UK strain. It is highly infectious. We need to do this now to avoid a longer lockdown," Queensland state Premier Annastacia Palaszczuk said.

"We've seen what's happened in other countries. I don't want to see that happen to Queensland, I don't want to see that happen to Australia."

Australia has been relatively successful in curbing the spread of Covid-19, with just over 29,000 cases and 909 deaths during the pandemic to date.

However, the country's vaccine rollout has been sluggish, with just over 500,000 shots administered so far in a country of 25 million -- falling far short of a government target to vaccinate four million by the end of March.

Palaszczuk said lockdowns would "be part of the Australian way of life until everyone is vaccinated".

Unlike countries such as the United States and Britain, Australia did not grant emergency approval for any vaccines and waited until late-February to begin inoculations.

Progress was hampered further by delivery issues, including Italy's landmark decision to block the export of 250,000 Covid-19 vaccine doses.

But while many Brisbane residents support the lockdown, business owners were concerned about the impact on trade with restaurants and bars forced to close from 5 pm local time Monday.

Katherine Pullos, events and entertainment manager at three bars in the Fortitude Valley nightlife precinct, said the announcement was "heartbreaking" and the measures bordering on "draconian".

"It will affect our trade next weekend and in the weeks to come until public confidence gets up again," she told AFP. "It frightens the heck out of people."

Schools have also been closed but people are allowed to leave home for essential work, to buy food, exercise and for medical care.

'Has to be done'

The lockdown comes just ahead of the Easter long weekend beginning Friday, throwing school holiday plans into chaos as several states closed their borders to Brisbane.

Before the announcement, Brisbane was among several Australian cities enjoying relaxed restrictions with residents able to freely attend events including concerts and sporting fixtures.

Cameron Dolbel, who works at a city sports bar, said he would have no income until the lockdown was lifted and the venue reopened.

"It sucks but it has to be done. You have to look after the people," he told AFP.

Shoppers rushed to stock up ahead of the lockdown, despite authorities urging against panic buying, stripping shelves in some supermarkets of toilet paper, milk and bread.

Wearing masks in public is also becoming mandatory across Queensland after one infectious person travelled to the regional town of Gladstone.

The number of international flight arrivals to the state will be halved to ease pressure on hospitals, which are also dealing with a surge in Covid-19 cases from neighbouring Papua New Guinea.