The South Australian premier has moved to tighten density limits and reduce family gatherings after the state posted a record 774 new infections.
Steven Marshall said he would move quickly to ensure new daily infections wouldn't descend into the thousands over the coming days and weeks.
"It will overwhelm our health systems right across the country if we don't take action," he said on Sunday.
"We've got to swing into action to save lives."
Indoor hospitality will go to a one person per four square metre rule and outdoor activities will be allowed one person for every two square metres.
Gyms will be restricted to one person for every seven square metres.
Family gatherings will be reduced from 30 to 10 people.
"There is no doubt this is going to be a very tough time for South Australia," Mr Marshall said.
People arriving from interstate won't need to take a PCR test before arriving but are being told to take a rapid antigen test after entering SA.
