Australian police have arrested two men accused of planning an anti-lockdown protest in Melbourne, an unusual move to stop an event that authorities said would put "lives at risk".

Police said Friday that the two men in their 40s had been detained after mobile phones and a computer were seized and both would be formally charged with inciting a criminal offence.

The pair were arrested following an investigation into a protest of hundreds of people planned for Melbourne city centre on Sunday, police told AFP.

The gathering would breach Melbourne's wide-ranging lockdown -- which entered into force Thursday, banning large gatherings and preventing residents from going outside except to work, exercise or buy essentials.

The state of Victoria -- which includes Melbourne -- recorded 450 new virus cases on Friday and has seen record deaths this week, making it Australia's most serious outbreak.

Police in Victoria have vowed to crack down on anyone breaking lockdown restrictions, issuing 196 fines in the past 24 hours for everything from failing to wear a mask to breaching an overnight curfew or collecting a pizza.

The state of Victoria -- which includes Melbourne -- recorded 450 new virus cases on Friday and has seen record deaths this week, making it Australia's most serious outbreak
The state of Victoria -- which includes Melbourne -- recorded 450 new virus cases on Friday and has seen record deaths this week, making it Australia's most serious outbreak AFP / William WEST

But the decision to arrest the pair marks an escalation amid a series of legal battles over Black Lives Matter and other protests.

Since the pandemic began, Australian authorities have tried to proscribe a series of political gatherings on health grounds, with mixed legal success.

That has fuelled intense debate about whether the right to protest and freedom of speech are being unfairly curtailed, or whether public health concerns should take priority.

A Facebook page for the Sunday protest has been taken down, but it had voiced opposition to the forced closure of small business, mandatory mask wearing and "mandatory vaccines".

Many of the Australian government's measures to tackle the pandemic have sparked conspiracy theories and been opposed by anti-vaccination activists, self-styled "sovereign citizens" and a plethora of other anti-government movements.

The country of 25 million has so far recorded more than 20,000 virus cases and 255 deaths.