South Australia will reopen its borders to unrestricted travel on July 20, while restrictions on venues including pubs, restaurants and gyms will be further eased next week.

From next Friday, up to 300 people will be allowed in venues, with up to 75 per room.

Premier Steven Marshall said the decision to lift border restrictions means travellers into South Australia from other states would no longer need to quarantine themselves for 14 days.

“We don’t want to unnecessarily detain people for two weeks of isolation if they don’t pose a health risk to us in South Australia,” Mr Marshall said.

By the time they reopen, South Australia’s borders will have been shut for almost four months after the closure came into effect on March 24.

However, Mr Marshall said restrictions for international travellers will remain.

The move follows Prime Minister Scott Morrison urging states to reopen their borders at Friday’s National Cabinet meeting.

“I made clear to the states and territories today, if someone can’t come to your state from Sydney, then someone can’t come to your state from Singapore,” Mr Morrison said.

“If you want to open up borders for international students, then you have to open up borders for Australians.”

Mr Morrison also announced sporting events and festivals could soon be allowed to have up to 10,000 people in attendance if they were seated and ticketed.

Singapore Airlines flights to Adelaide resumed this week, but mostly for cargo and those who have an urgent need to travel.

The Premier also revealed the state government was seeking legal advice on whether it could open particular state borders earlier than July 20.

“We will be looking at some of the state borders with individual jurisdictions who are doing particularly well,” he said.

“We don’t want to unnecessarily detain people for two weeks of isolation if they don’t pose a health risk to us in South Australia.

“We’re just getting some final legal advice on that.”

More relaxed restrictions have been brought forward in South Australia.

Stage three accelerated

South Australia’s 75-person per room limit, beginning next Friday, will also apply to gymnasiums, but smaller limits will continue to apply for fitness classes.

Mr Marshall described the new rules from next Friday as “stage 2.5” of the state’s easing of restrictions and announced the move to stage three will be brought forward from July 3 to June 29.

Stage three was supposed to include a cap of 100 patrons in any one room, but Mr Marshall said on Friday that limit would be scrapped in favour of one person per four square metres.

“That is a movement that we are making here in South Australia, and I think that it is going to be a movement that we make right across the country,” he said.

Stage three changes will include reopening Adelaide’s casino and gaming venues, indoor playgrounds and amusement arcades.

But nightclubs and music festivals will remain off limits.

On Friday morning, the Australian Hotels Association called for bigger crowds at pubs, saying the industry was “still in crisis”.

“There’s tens of thousands of our staff who have not been re-engaged yet … we actually can’t get them back until we get the capacity of people coming in and spending the money,” state chief Ian Horne said.

Mr Marshall said the decision to reopen the state’s borders was only possible because of high levels of compliance with coronavirus restrictions in South Australia and a “massive improvement right across the nation”.

“We still have a very, very high level of compliance … this has given us great confidence that we can continue to lift restrictions in South Australia,” he said.

“There have only been 43 [COVID-19] cases over the past week right across the entire country with more than two thirds of those coming from people just returning from overseas.”