SA has declared the greater Brisbane area a coronavirus hotspot, preventing people travelling from the region unless they are a returning resident or someone relocating permanently.

But the state's transition committee has confirmed changes to SA's density rules and the size of gatherings in time for Easter.

From Wednesday the one-person-per-two-square-metres requirement changed to three-people-per-four-square-metres.

The move allows pubs, clubs, restaurants and other venues to cater for up to 75 per cent of their capacity.

The state has also lifted patron caps on venues such as churches, theatres and cinemas from 75 to 100 per cent, but all people must wear masks.

The changes apply to venues with fixed seating and with a limit of 1000 people.

Larger venues continue to need a specific COVID-safe plan.

SA reported three new coronavirus cases on Tuesday, all in people who recently returned from overseas.

Tests are underway to determine if they are old infections.

Australian Associated Press