New daily cases climbed to 2465 on Thursday after days of about 200 cases, and South African Health Minister Joe Phaahla said the variant was linked to an "exponential rise" of cases in the past few days.
The origin of the strain remains unclear, but beyond South Africa it has been observed in people in Belgium, Botswana, Hong Kong and Israel.
The World Health Organisation on Friday named it "a variant of concern", and termed the new strain "Omicron" after a letter in the Greek alphabet.
Scientists believe it has about 30 mutations in the coronavirus' spike protein, which could affect its infectiousness.
The United States has already moved to restrict travel from South Africa, while Canada is closing its borders to affected countries and the UK and EU are introducing flight bans.
Vaccine maker BioNTech is expecting more data on the new variant within two weeks to help determine whether its vaccine produced with partner Pfizer needs to be reworked.
The companies said on Friday they would expect to be able to ship a new vaccine tailored to the emerging variant in approximately 100 days, if necessary.
Victoria reported 1252 COVID-19 cases and five deaths on Saturday.
The figures bring the total number of active infections in the state to 11,257.
NSW recorded 235 new infections, and no further deaths in the 24 hours to 8pm on Friday.
Meanwhile, Papau New Guinea police and Australian authorities are in Honiara, responding to a request from the Solomon Islands government.
The Australian-led effort to restore calm follows days of rioting, with many protesters coming from the province of Malaita, where there is resentment toward the government in Guadalcanal province and opposition to its 2019 decision to end diplomatic ties with Taiwan and establish formal links with China.
*This edition of The Informer was written by The Canberra Times journalist Miriam Webber. If you'd like to show your support for the team behind The Informer, why not forward us to a friend?
THE NEWS YOU NEED TO KNOW
- Australia closes border to southern Africa
- Victoria records 1252 COVID-19 cases, five deaths
- NSW teachers headed for strike action
- Explainer: What we know about the new COVID-19 'variant of concern' Omicron
- NSW records 235 COVID cases
- 'I don't understand': Canberra 'hitman' accused of NSW doorway murder
- Ocean wind farms on horizon for Australia
- Volunteer firefighter 'feared for life' when loaded rifle was pointed at group