Australia's Queensland state enforced a three-day lockdown in Brisbane, the state capital, from Friday evening after a hotel quarantine worker tested positive for the more contagious variant of Covid-19 that has emerged in Britain.
The Australian government also announced that it will begin pre-flight screening for passengers from the UK as well as cutting flights from Britain by half and ordering all visitors to the country to wear masks.
The decision to temporarily shut down 2 million people came hours before a special national Cabinet meeting called to respond to the new strain from the UK.
The Cabinet will discuss further proposals from an expert medical panel to tighten rules for international travellers.
Prime Minister Scott Morrison described the situation in Brisbane as "serious".
Residents of Australia's third most populous city must wear masks and can go outside only for one of four essential reasons – grocery shopping, work, exercise or medical treatment.
Annastacia Palaszczuk, the Queensland state premier said: "We know that this UK strain is highly infectious. It is 70 per cent more infectious, and we are going to go hard and we are going to go early to do everything we can to stop the spread of this virus."
"If we do not do this now, it could end up being a 30-day lockdown," Ms Palaszczuk said.
Australia is on course to begin administering the first Covid-19 vaccines in February as it tries to contain the spread of infections in its largest cities of Sydney and Melbourne.
Queensland state reported no new local cases on Friday, but the UK variant case has sparked fears of a wider outbreak. Victoria, the country's second-most populous state, reported no cases for the second straight day.
Australia has reported a total of just over 28,500 Covid-19 cases and 909 deaths since the pandemic began, with border closures and speedy tracking systems helping keep numbers relatively low.
