Covid-19 Sydney cluster: 30 new cases reported overnight

New South Wales has reported 30 new cases overnight, with 28 linked to the Northern Beaches cluster.

The New South Wales Premier, Gladys Berejiklian, says while the number are higher than yesterday, a positive is that officials haven't seen evidence of the virus spreading significantly outside the Northern Beaches.

Everyone in the Greater Sydney area, including the Blue Mountains and Central Coast, is now asked to have no more than 10 people in their homes until Wednesday.

The Northern Beaches region remains in lockdown.

The New Zealand government says it is monitoring the new Covid-19 cluster in Sydney closely but it is too early to say if it will affect a trans-Tasman bubble.

From today, the neighbouring state of Queensland is requiring arrivals to have a border pass and get tested for the coronavirus.

Tasmania requires anyone coming from the state to spend 14 days in quarantine - but anyone who has been in Sydney's Northern Beaches is banned.

Western Australia is reimposing its hard border, so no-one can travel there from New South Wales.

WA's Premier Mark McGowan said while he regrets having to take the step less than a week before Christmas, the risk of Covid-19 emerging in the community is too high.

"I know these changes are going to be hard to take for many people," McGowan said at a press conference last night.

"I know it will throw Christmas and reunion plans into disarray if it hasn't already.

"These are now extraordinary circumstances.

"I wish I didn't have to be making this announcement but as Premier I have a responsibility for every Western Australian and I need to do what is right to keep our state safe and strong."

McGowan said it was not known how long the border would stay up.

"We hope it's only for a short period and we can reassess our border controls when the health advice says it's ok to do so," he said.

He advised West Australians to reconsider travel to New South Wales.

"WA's community has been Covid-free 252 days. I want to keep it that way," he said.

"I want to protect people's health and, in turn, protect people's jobs.

"If you can avoid it, please don't go."

NZ monitoring situation in NSW

The New Zealand government says it is monitoring the new Covid-19 cluster in Sydney closely but it is too early to say if it will affect a trans-Tasman bubble.

"As previously stated, a travel bubble won't start until the first quarter of 2021," a government spokesperson said in a statement.

"Commencement is dependent on no significant change in the circumstances of either country.

"Decisions on whether or not to proceed with a travel bubble will occur in the new year and we will assess the situation at that point.

"We're monitoring the situation closely, but it's too early to make any decisions based on the current community cases in New South Wales."

In a statement released this afternoon, Ministry of Health officials said they are closely monitoring the situation in New South Wales and are in regular contact with Australian officials.

It also commented on news New South Wales is also implementing new measures for international aircrew.

"Officials in New Zealand have already increased public health and testing measures relating to aircrews to further strengthen our country's defence against Covid-19.

"Among the measures, overseas-based air crew are required to stay in a managed isolation facility for the duration of their layover while in New Zealand."