“We do from a health perspective want to include country SA in the lockdown and it’s not fair for them if they don’t have that disaster income support,” Mr Marshall said.
“So that will be extended state-wide.”
South Australia recorded one new COVID-19 case as the state entered its first full day of lockdown and the list of potential COVID-19 exposure sites linked to a new cluster continued to grow.
SA Police Commissioner Grant Stevens said on Wednesday morning the case is a person who went to the Burnside Village shopping centre in Adelaide's west.
The new case brings the total number of infections to six, and will be included in the daily numbers announced later on Wednesday.
The Premier has also announced a $100 million dollar state-wide support package for small to medium size businesses.
“This is going to support businesses that are suffering very significant reductions in their turnover because of these restrictions.”
“The number one focus is getting on top of the health issues in South Australia so we can open up for business again.”
Premier Marshall says compensation will likely be extended if the lockdown continues beyond seven days.
Australian Defence Force personnel are set to assist with swabbing at Covid-19 testing clinics in South Australia in an effort to reduce long wait times.
South Australia’s chief health officer Nicola Spurrier says interstate nursing staff have also been enlisted as the number of exposure sites grows.
South Australia enters seven-day lockdown
It comes after five cases were reported in the emerging cluster by Tuesday afternoon, with officials declaring the next 24 to 48 hours crucial to prevent virus infections running wild.
The fifth case, a man in his 60s, dined at a restaurant in Adelaide where previously infected people were also present on Saturday night.
They had all attended a birthday party in a private function room which authorities said had the potential to act as a superspreader event.
During the week-long lockdown, which began at 6pm local time on Tuesday, South Australians will only be allowed out for five reasons - to provide essential care, to seek medical assistance, to buy essential food and other goods, for essential work, or to exercise for up to 2.5 hours.
Mr Marshall said it was vital for SA to "go hard and go early" to have any chance of containing the outbreak.
"We hate putting these restrictions in place but we have one chance to get this right," the premier said.
"We are moving as quickly as we can to slow and stop the spread of this cluster.
"We know these restrictions will take a heavy toll. But we've always had a situation where we go hard and we go early in South Australia.
"We've got to stop movement around this state and we've got to stop it immediately."
The new SA cluster began with an 81-year-old man, who entered the country from Argentina, his daughter and another two men.
He had returned to Australia via NSW, where he spent 14 days in quarantine.
He arrived back in SA on 8 July and presented to a suburban hospital over the weekend after developing symptoms.
All the confirmed cases are known to the man or his extended family.
Additional reporting by Peta Doherty.