South Australians who breach self-isolation or quarantine orders will be slapped with a $1000 on-the-spot fine under new regulations rushed into force.
Fines of $5000 can also be imposed on companies and businesses that trade against the current rules and come as SA's total number of coronavirus cases rose by 30 on Saturday to 287.
Police Commissioner Grant Stevens said while the vast majority of people were doing the right thing, some were not complying.
"This will send a very strong message that people who don't comply will face a stiff penalty," he said.
"The principal objective here is to ensure that people who are required to self-quarantine, who we believe are at risk of spreading the infection, comply with those obligations."
Before the new rules, police could take action against those flouting the rules but were required to launch a formal prosecution and take the matter to court.
New regulations in SA will also ban gatherings of more than 10 people as part of social distancing rules while the government has closed emergency departments at country hospitals where they are co-located with aged-care facilities.
Commissioner Stevens said he appreciated that things were changing rapidly.
"We would hope that people appreciate the dynamic nature of this incident that we're dealing with," he said.
"These are unique and unprecedented circumstances. We are writing the rules for this thing every single day."
Chief Public Health Officer Nicola Spurrier said the vast majority of SA's cases were still linked to people who had travelled interstate or overseas or were close contacts of other cases.
Only four were considered to come from wider community transmission.
Of the virus patients in hospital, five were still in intensive care and three of those were listed as critical.
A 53-year-old woman who was previously admitted to ICU has since improved and been moved to an isolation ward.
With Easter and school holidays approaching, Professor Spurrier said all South Australians were urged to holiday at home this year.
Premier Steven Marshall said Kangaroo Island was particularly off-limits to tourists, warning that a widespread outbreak of COVID-19 there would prove difficult for emergency services to handle.
Mr Marshall said the government understood that the restrictions were changing people's lives.
"But they are not optional," he said.
"Everyone needs to understand that from today failure to follow the directions to the letter of the law will leave individuals and businesses liable for significant on-the-spot fines.
"The period of education regarding restrictions during this pandemic really has come to end and the period of enforcement has begun."
Australian Associated Press