SYDNEY - As the number of COVID-19 cases jumped to over 150 in Australia on Friday, Prime Minister Scott Morrison suggested Australians reconsider their need to travel overseas.

The prime minister also said that he would be advising against gatherings of more than 500 people as of Monday.

"We now advise all Australians to reconsider your need to travel overseas at this time -- regardless of your destination, age or health, if your travel is not essential, consider carefully whether now is the right time," Morrison said.

Morrison described the move to reduce mass gatherings as a precautionary measure which does not include schools, universities and airports, and added that he would still be attending a football match as a spectator over the weekend.

"The goal here is very straightforward.. it is simply to slow the rate of transmission of the Coronavirus within Australia," Morrision said.

"This is incredibly important because as we slow it, as we manage it, that ensures that the national health system.. will be able to accommodate the increasing demands that we'd expect to see as a result of the Coronavirus spread."

Earlier in the day, the Australian Grand Prix, scheduled to take place in Melbourne over the weekend, was cancelled after a racing team member was tested positive for COVID-19.

Also the first of a series of international cricket matches between Australia and New Zealand got underway in front of an empty stadium, with spectators banned due to health concerns.

Shortly after, Australia's chief medical officer Brendan Murphy recommended that the government introduce a ban on all events with crowds of over 500 people.

"All the international evidence suggests that if you have some community transmission the way in which it can be spread more rapidly is in very large events," Murphy said.

You might only have one or two people who might be carrying the virus and the chances of it being spread at those large events accelerate the rate of progression of this virus."

The country's state and federal leaders, known as the Council of Australian Governments (COAG), gathered in Sydney to discuss the advice and establish a unified response to the virus.

It was there that Morrison revealed he would be advising against non-essential overseas travel, as well as mass gatherings, but that decisions regarding specific events would remain in the hands of State leaders.

Meanwhile, the State of New South Wales (NSW), of which Sydney is the capital, remained the hardest hit by the disease with 77 confirmed cases.

NSW's Chief Health Officer Kerry Chant warned that 1.5 million people in the state are likely to be infected with the virus and called for more widespread testing of the disease.

In the State of Queensland, where earlier in the week Hollywood actor Tom Hanks was diagnosed with COVID-19, health officials also warned of a sharp increase in cases over coming months.