Melbourne’s escalating COVID outbreak has prompted the state government to cap crowds at the Australian Open.

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 said that all tickets already purchased remained valid and none would be cancelled. Nor is there any change to ground pass access.

The decision was made after Victoria reported 37,169 COVID cases 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.

“Ventilation will be improved in indoor areas of Melbourne Park, with HEPA filters to be installed in some spaces after a ventilation assessment is completed for the venue,” a state government release said on Thursday.

“As COVID-19 hospitalisations and cases continue to rise in Victoria, these mitigation strategies are proportionate and designed to assist in limiting the spread of COVID-19.”

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.

-with AAP