Authorities extended a COVID-19 lockdown to include all of Sydney and surrounding population centers on Saturday as Australia's biggest city battles a surge in the highly contagious Delta variant of the coronavirus.

"From 6 p.m. today all of Greater Sydney, the Blue Mountains, the Central Coast and Wollongong will go into lockdown," said Gladys Berejiklian, the premier of New South Wales state, of the two-week restrictions.