Fans were forced to leave Rod Laver Arena with Novak Djokovic's third-round match at the Australian Open still in progress.
With Victoria entering a five-day lockdown from Saturday due to coronavirus concerns, spectators were told to leave Melbourne Park before 23:30 local time (12:30 GMT).
Restrictions were coming into place in Victoria from 23:59 local time (12:59 GMT).
Djokovic's clash against Taylor Fritz was the only match still in progress, although fans were informed to leave amid increasing drama. The world number one led by two sets to one but was struggling with a suspected abdominal injury in the fourth.
There were boos when the announcement was made, with a message also displayed inside the arena. Play was briefly suspended as fans were moved out.
No spectators will be allowed at the year's first grand slam for the next five days, although the tournament will continue.