No new cases of COVID-19 in Western Australia after first day of lockdown

There are no new cases of COVID-19 in Western Australia after the region's first night under a strict new lockdown.

On Monday afternoon, Western Australia's premier Mark McGowan revealed there are no new community cases, nor any in isolation, following a hotel worker's positive test on Sunday.

He says WA has seen a significant increase in testing since the worker contracted the virus. 

"There have been 3171 tests yesterday - the majority in the afternoon and evening - normally we only have 500 on a Sunday so that's a huge increase," he said.

Thirteen of the workers' close contacts have tested negative, and 11 of the contacts deemed to be "high risk" have been moved into hotel quarantine. 

So far, 66 close contacts have been identified.

Australia's fourth-most populous city had recorded no cases of the virus for 10 months, and Australia just hours earlier had announced 14 days without a locally acquired infection.

McGowan says the government is working with police to investigate how the hotel worker contracted the virus. 

The Perth metropolitan region, Peel and the South West will remain under lockdown until at least 6pm on Friday

Masks are also now mandatory across the region, including in the workplace.