A woman in her 30s who died of coronavirus in Sydney over the weekend has been identified as a 38-year-old Brazilian national with no pre-existing medical conditions.

Premier Gladys Berejiklian announced the death on Sunday and extended her condolences to the woman's family.

"I want to extend my heartfelt condolences to those families, the loved ones who are grieving today," she said.

NSW's deputy chief health officer Jeremy McAnulty said the woman was in her late 30s and was from central Sydney.

She died at Royal Prince Alfred Hospital in Sydney's inner west.

She was later identified as Adriana Midori Takara, an accounting student who spiralled quickly after contracting the virus, with shocked friends paying tribute.

Marlene Coimbra, who knew Takara, told The Daily Telegraph she was "mortified" by the news and her friend's condition deteriorated quickly.

"The virus debilitated her very, very quickly. It's shocking.

"She was healthy, happy, working, she had a boyfriend. It's shocking."

In another Facebook post, she was grieving "the loss of not a number but a sister and a friend".

"Adriana is a daughter, sister, aunty, niece and specially a friend. An amazing friend, not only my friend but friend of so many people," she said.

"Adriana is not a number, she is a woman with dreams and wishes.

"Tonight when you look at the sky, it will be brighter and the shiniest star will be my friend is peace away of all this madness (sic).

""I can't thank enough all the doctors for doing their best."

A migration agent who knew Takara told The Sydney Morning Herald "all goodbyes were said via Zoom to audiences in Australia and Brazil".

Another woman, aged in her 70s, also died from the coronavirus disease, the officials said.

The older woman was from south west Sydney and died at Campbelltown Hospital.

Berejiklian said the younger woman's death underscored that Covid-19 can be very dangerous even to young and healthy people.

NSW Premier Gladys Berejiklian on Sunday in Sydney. Photo / Getty

"If anybody think this is a disease just affecting older people, please think again," she said.

Berejiklian said the younger woman's death underscored that Covid-19 can be very dangerous even to young and healthy people.

"If anybody think this is a disease just affecting older people, please think again," she said.

New South Wales experienced a record of more than 100,000 tests after registering two deaths and 141 new locally acquired cases of Covid-19.