NSW residents urged to avoid travel to Adelaide as the state's coronavirus cluster grows

New South Wales residents have been advised to avoid travelling to Adelaide unless it is for an essential reason, as Adelaide residents are also urged to steer clear from entering the state unless absolutely necessary.

Speaking on Today, NSW Health Minister Brad Hazzard said travel advice had been revised and no one should be travelling to Adelaide until the state regained control of its coronavirus outbreak.

"Anybody who is thinking of travelling to Adelaide, it might be wise if you don't for the time being unless it's essential business or very important family business but even then be extremely cautious," he said.

READ MORE: South Australia confirms more coronavirus hotspots

"Obviously the South Australian government is trying to deal with an issue which is a challenge at the moment.

"We feel that they will be able to keep it under control and just a basic warning - don't travel unless you have to.

"And I have to say to our friends in Adelaide, don't come to NSW unless you really have to - family or really imperative business. Don't come until things are sorted."

Adelaide's coronavirus cluster in the city's north has ballooned to 20 cases of COVID-19.

Victorian officials have also requested all non-essential travel from South Australia into Victoria not go ahead.

READ MORE: How Adelaide's coronavirus cluster started and spread

Mr Hazzard confirmed the border would stay open for the time being.

"We are very keen to stay open," he said.

"We are keen for our families to be able to travel, if necessary, down to Adelaide but we don't want them doing it on a whim at the moment."

NSW has recorded its 11th day of no coronavirus community transmission.

Mr Hazzard said he has not spoken with Queensland's new health minister, but reiterated he hoped the state would open up to NSW.

"My focus has been on South Australia and Victoria at the moment," he said.

"I would say this to Queensland - I'm hoping you will open up."