Victoria is closing its border to New South Wales after confirming two further cases of COVID-19 in one day.

It makes for a total of five new cases in Victoria on Thursday, and three on Wednesday.

Acting premier Jacinta Allan said the two new positive cases came as a result of the testing program that was underway.

The cases were close contacts of the known positive cases to date.

More than 70 people are now in isolation as a result of Victorian cluster.

Ms Allan said the public health team was doing extensive work to track their movements and exposure sites.

Victoria's border with New South Wales closes at 11:59pm on January 1.

"This is not an easy choice and certainly not one we wanted to be making and announcing on a day that is supposed to be about celebrating," Ms Allan said.

But she said Victoria had to remain vigilant and keep ahead of where the case numbers might be, particularly in light of the case numbers coming out of New South Wales.

New South Wales today announced 10 new cases of community transmission.

The Victorian government has again called on any of the state's residents visiting in New South Wales to get home.

Wollongong and the Blue Mountains will be added to Victoria's list of red zones after 11:59pm today.

The rest of New South Wales will be red zoned as of midnight on Friday.

Ms Allan said any Victorians coming home would need to get COVID tested and go into isolation for 14 days.

"Obviously this is going to cause some disruption for Victorians who are holidaying," she said.

"We do apologise for this disruption, however these difficult decisions are about protecting our community, protecting and keeping low the case numbers in our community, and doing everything we can to lock in the gains we've made over the course of 2020, so we can move into 2021 and have a much better year."

EARLIER:

VICTORIANS planning a New Year's Eve party at their homes tonight will need to reduce the number of invitees from 30 down to 15, as new restrictions come into effect.

It comes following new confirmed COVID-19 cases in the state.

From 5pm today, the limit for people gathering in private homes will be reduced from 30 to 15.

"So, if you are planning a party tonight you will need to reduce your numbers from 30 down to 15," acting premier Jacinta Allan said.

Masks will also be mandatory indoors from 5pm tonight in any location that's not your private home.

Three new COVID-19 cases were confirmed on Wednesday evening, ending Victoria's 61-day streak without community transmission of the virus.

Three further cases have been identified.

There are 10 active cases of COVID-19 in the state.