Finance Minister Mathias Cormann has warned a second wave of coronavirus could cost the Australian economy $80 billion over the next two years.

His calculation came as global share markets erupted into a sea of selling on fears of a pandemic resurgence, killing off recent optimism for a quick economic recovery.

The Australian share market looks set for a three per cent tumble at the opening on Friday after the Dow Jones index on Wall Street slumped over six per cent, posting its wost day since mid-March.

The local share market also fell three per cent on Thursday.

The Morrison government is worried last week’s anti-racism rallies, and more marches scheduled for this weekend, will spread the virus.

Senator Cormann said the protests were putting lives and livelihoods at risk.

“If we had a second wave of infections it would cost our economy about $80 billion over the next two years,” he told Sky News.

“We are in the middle of a health emergency, this is not over and people who choose to attend those rallies are putting the lives and jobs of their fellow Australians at risk.”