New South Wales has recorded 89 new community cases of Covid-19, taking Sydney's outbreak to a total of 767 injections.

Of today's cases, 75 are linked to a known case or cluster and 21 cases were infectious in the community.

A man in his 70s who lived in Sydney's eastern suburbs and was a confirmed Covid-19 case has died, NSW Health said.

There are currently 65 cases in hospital, with 21 in intensive care and four on ventilators.

NSW Premier Gladys Berejiklian said that while it was pleasing to see daily cases drop back to double digits, a single day's figures doesn't indicate a trend.

"In the next few days we want to see those numbers go in the same direction," she said. "One day is not a trend... Our efforts will allow us to leave the lockdown in a timely way, but that is dependent on all of us doing the right thing at all times."

Government 'lost control' of outbreak

NSW Deputy Premier John Barilaro said earlier today the state government "lost control" of the latest outbreak and could have locked down Greater Sydney a week earlier.

Barilaro told the ABC the government followed health advice, but there was "no question, last week we lost control of the Delta strain".

"Hindsight is a beautiful thing. Absolutely you could have gone a week earlier, three days earlier, four days earlier, but the reality is ... that wasn't the advice," he said.

NSW Deputy Premier John Barilaro. (Photo / Getty)

Defending the government's actions, Barilaro said there was "no rulebook" on how to respond to outbreaks of Covid-19 and that the state was dealing with something it had never encountered before with the Delta variant of the virus.

"The difference here is the Delta strain was much more infectious and transmissible than the previous virus, and the previous pandemic outbreak, and what we did is make the decisions, we went into tight restrictions and into lockdown," he said.

The situation had now gotten "out of control" and the government was "working with our community to make sure we get on top of it so we can come out of lockdown sooner rather than later," he said.

When asked why so many seemingly non-essential shops were allowed to remain open during lockdown, Barilaro said the government had never chosen what stores are considered essential "because everyone has different needs at different times".

Dire lockdown prediction

Sydney's lockdown could last until the end of August, one expert says, pointing to the difficulty Melbourne experienced getting its cases down during its second lockdown.

NSW Premier Gladys Berejiklian acknowledged yesterday it would be "almost impossible" for authorities to lift the lockdown on Friday as scheduled.

While the state has not yet revealed how long any extension would be, some experts have suggested it could last between three to four weeks.

Sydney's lockdown restrictions are set to be extended beyond this Friday. (Photo / Getty)

Professor Michael Toole, a leading epidemiologist at the Burnet Institute pointed out Melbourne took six weeks to get its Covid cases down to almost zero from around 100 during its second lockdown last year.

The city — which endured a three and a half month lockdown last year — recorded 100 cases on August 30, 2020.

"It reached almost zero on October 14, so it took six to seven weeks, and that was with the strictest possible restrictions," Toole said.

Greater Sydney's current restrictions are not yet as strict as Melbourne's lockdown rules, which included a curfew, 5km travel limit and the closure of non-essential retail shops.

NSW outbreak reaches Melbourne

Victoria has now confirmed three new Covid-19 cases.

Victoria's Covid Commander Jeroen Weimar said three of a family of four from the City of Hume in Melbourne arrived on a flight from Sydney on July 4 carrying red zone permits.

The other person entered Victoria by road on July 8.

They all initially tested negative after arrival but two became symptomatic and were tested on Sunday with a positive result recorded on Monday morning. A third member of the household tested positive today and was isolating throughout their infectious period.

Adding to the tension is the positive test of two members of a removalist crew who travelled through Victoria and South Australia.

Three removalists, two of whom have tested positive to Covid-19, arrived in Melbourne on Thursday to deliver furniture to two households, one in Craigieburn and one in Maribyrnong.

They then stayed overnight in Melbourne before heading to South Australia on Friday morning. Ariele Apartments in Maribyrnong has been put into lockdown as a result.

The cases come after Victoria recorded its 12th day of no community cases and the state effectively shut the border to NSW and the ACT overnight, declaring them red zones under the travel permit system.