The case's source of infection remains under investigation, having first been reported on Thursday.

Earlier on Friday, Queensland Premier Annastacia Palaszczuk announced Greater Brisbane would enter into a rapid three-day lockdown after a cleaner at a quarantine hotel was diagnosed with the highly-contagious UK strain of COVID-19.

On Friday night the NSW government put in place a new Public Health Order requiring anyone in NSW who had been in Greater Brisbane since 12:01am on January 2 to follow the same lockdown rules.

Travellers from the area will only be able to leave their house or accommodation for five reasons until 6pm on Monday - to obtain food or essential shopping, exercise, work if they cannot do so from home, undertake caring duties or seek medical care.

People who have arrived in NSW after transiting through Brisbane Airport will not be subject to the requirements.

Queensland's case on Friday prompted Prime Minister Scott Morrison to reduce the number of international arrivals into NSW, WA and Queensland's hotel quarantine systems by 50 per cent.

A weekly cap in NSW has been set at 1505 people until at least February 15.

He also announced that overseas travellers would need to test negative to COVID-19 before departing for Australia, and daily coronavirus testing was now required for quarantine workers.

"This virus continues to write its own rules, and that means that we must continue to be adaptable in how we continue to fight it," Mr Morrison said on Friday.

As well as four local COVID-19 cases, NSW also recorded seven cases in returned travellers from more than 26,000 tests in the 24-hour period to Thursday at 8pm.

Acting Premier John Barilaro said that testing number is on the "low side".

One reported case is linked to the Croydon cluster in Sydney's inner west and two are linked to the Berala cluster. All three are close contacts of previously-reported cases and were in isolation.

In total there are 11 people in the Croydon cluster and 20 in the Berala cluster.

The suburbs north of Narrabeen Bridge on the northern beaches, meanwhile, have been under stay-at-home orders since before Christmas but the restriction is due to be lifted from Sunday.

Mr Barilaro said NSW authorities were working with their counterparts in Queensland but the state was not considering a hard border.

"At no point during this pandemic have we ever had a kneejerk reaction or treated the border like a light switch," he told reporters.

A number of $200 fines have been issued in NSW to people not wearing masks including a 41-year-old man in Campbelltown who told police "it's a joke".

A 28-year-old female director of the Pyrmont establishment which hosted a controversial wedding - for a bride from the northern beaches - was also fined $5,000 after breaching a number of health orders.

The wedding has prompted 22 fines in total.

The unsourced northern beaches case has prompted new health alerts at Woolworths in Avalon at certain times between January 2 and January 6 and a Chemist Warehouse for 15 minutes to 1.15pm in Avalon on January 3.

Anyone who attended those venues at the times listed must immediately get tested and self-isolate until a negative result is received.

Chief Health Officer Dr Kerry Chant said the man did not present symptoms until after he completed quarantine, at which point he sought re-testing.

Elsewhere, the Service NSW app, which hosts a mandatory check-in system for hospitality venues, stopped working for several hours on Thursday afternoon.

It has been compulsory to use the app in some businesses since the start of 2021.

The second day of the Australia-India Test is also being played at the SCG on Friday, with attendees forced to wear masks except when eating or drinking.

Australian Associated Press