Five million Sydneysiders will be banned from coming to Queensland.
Greater Sydney has been added to the announced COVID-19 hotspots list by Queensland.
Local government areas Fairfield, Liverpool and Campbelltown in west Sydney were declared hotspots earlier this month after several community transmission outbreaks.
A further 31 Local Government areas will be added to the hotspots list from 1 am on Saturday.
On Wednesday another 19 cases were confirmed in New South Wales as more possible cluster sites identified as suburbs in east Sydney.
It comes as Queensland faces its own imminent coronavirus crisis.
Two young women tested positive south of Brisbane after returning from coronavirus-stricken Melbourne for eight days at the hospital.
“We do not want a second wave here. We do not want widespread community transmission,” Premier Annastacia Palaszczuk told reporters.
Palaszczuk also announced that if group transmission takes place beyond Sydney, another hard boundary closure is on the cards.
Wednesday’s declaration means the border drives away non-Queensland citizens coming from the region.
Residents of Queensland are forced to quarantine in hotels at their own expense for 14 days.
Earlier, All of Victoria was declared a hotspot amid widespread disease transmission by the QLD government.