Australia's third-largest city of Brisbane and other parts of Queensland state will enter a COVID-19 lockdown starting Saturday as authorities race to contain an emerging outbreak of the Delta strain.

Millions of residents in the city and several other areas will be placed under stay-at-home orders beginning Saturday afternoon for three days, state Deputy Premier Steven Miles said.

In the "strictest lockdown" the city has enforced, residents will only be allowed to leave their homes for essential reasons including buying groceries and exercising.