Perth, capital of Western Australia, has begun a four-day lockdown today (Tuesday), joining New South Wales (NSW) capital Sydney and the northern city of Darwin, reports Reuters. Queensland will also impose a snap three-day lockdown in capital Brisbane and some neighbouring regions from today evening.

Australia's most populous state, NSW, has reported a slight rise in locally acquired Covid-19 cases, while officials tighten curbs to contain flare-ups of the highly infectious Delta variant in several other regions.

An outbreak in Sydney linked to the variant has grown to nearly 150 cases. Worries the strain could touch off major outbreaks have forced lockdowns in three major cities and some form of curbs in several others - affecting more than 20 million Australians, or about 80 per cent of the population.