Australia's third largest city will enter a three-day lockdown beginning late on Friday, as authorities seek to prevent the spread of a more contagious variant of Covid-19 first detected in Britain.

Brisbane's 2 million residents will be barred from leaving their homes for anything but essential business after a worker at a quarantine hotel in the city tested positive for the new strain of the virus, according to Reuters.

“If we do not do this now, it could end up being a 30-day lockdown,” state Premier Annastacia Palaszczuk said as she announced the lockdown.

People must wear masks when they leave home for essential business, Palaszczuk said.

Funerals and weddings can proceed, but with limits of 20 and 10 people respectively. Entertainment venues will close and restaurants and cafes will be allowed to provide takeaway only.