Australia ordered its citizens Wednesday to halt all overseas travel in an unprecedented move designed to choke off the spread of the coronavirus epidemic.

Prime Minister Scott Morrison announced at a press conference what he called an “indefinite ban” on foreign travel alongside a crackdown on indoor gatherings in Australia of more than 100 people.

“This is a once-in-100-year type event,” Morrison said of the pandemic. “We haven’t seen this sort of thing in Australia since the end of the first world war.”

“We are going to keep Australia running, we are going to keep Australia functioning, [but] it won’t look like it normally does,” he said, warning that the measures being taken would last at least six months.

Australia has so far recorded more than 450 confirmed cases of coronavirus, with the numbers escalating daily. There have so far been just five fatalities.

Morrison rejected calls for the government to order schools to close, as has been done in other countries, saying the impact on society and the economy from such a closure would be “severe”.

“Whatever we do we have to do for at least six months,” he said, adding that among other consequences a long school closure would remove 30 per cent of workers from the health industry as parents remained home with their kids.

The ban on overseas travel came as Australia’s two main airlines, Qantas and Virgin Australia, slashed international flights 90 per cent and 100 per cent respectively.

Acknowledging it was “the first time that has ever happened in Australia’s history”, he said the ban was needed to stop travellers from bringing more coronavirus cases into the country.

The ban on indoor gatherings of more than 100 people applies to “non-essential” gatherings and excluded public transport, shopping sites and school.

The government had already banned outdoor events of more than 500 people, dealing a severe blow to spectator sports in the sports-mad nation.