The Victorian government confirmed the decision on Thursday, with ticket sales for all sessions to be paused at 50 per cent capacity if they haven't already been sold to that level.

Organisers added all tickets already purchased remain valid and no ticket will be cancelled with no change to ground pass access.

The decision was made after Victoria reported 37,169 new cases of the virus on Thursday and 25 deaths.

As well as limited capacity, COVID-19 restrictions for the tennis grand slam will include face masks being mandatory for all patrons unless they are eating or drinking and social distancing measures of one person per two square metres at indoor hospitality venues.

The build-up to the Open, which starts on Monday, has been overshadowed by doubt surrounding the participation of defending men's champion Novak Djokovic.

The Serbian superstar was detained by Australian Border Force officials upon his arrival to Australia last week before being released on Monday after winning a court case against the Australian Government.

Djokovic's ability to play in the event remains unclear however as Immigration Minister Alex Hawke ponders using discretionary powers to cancel the world No.1's visa.

Australian Associated Press