Brisbane has entered a three-day lockdown after a cleaner at a quarantined hotel was diagnosed with the Covid-19 variant first identified in the UK.

Australia's third-largest city and its surrounding areas will also see the introduction of compulsory face masks for the first time, the Queensland state government said.

Queensland chief health officer Dr Jeannette Young said: "We know that that strain is 70% more infectious and we know the extreme difficulty that the UK has had in controlling their outbreak due to that strain.

"So we need to act really, really fast. We need to find every single case now."

The cleaner, in her 20s, is the first person to be infected with the variant in Australia.

Officials believe the woman was infectious from January 2 and tested positive after displaying symptoms on Wednesday.

Her diagnosis ends around four months of no locally acquired infections in the Queensland state.

Australia's prime minister Scott Morrison has announced that the country will be almost halving the number of plane passengers arriving in order to prevent the spread of the Covid-19 variant.

The arrival of limited international passengers to New South Wales, Queensland and Western Australia state airports will last until 15 February.