COVID-19 rapid testing technology has been sent to Mildura amid concerns the virus is rapidly spreading through the youngest cohort of the community.

At least three Sunraysia schools closed their doors on Friday following reports of additional positive cases while most of a "significant increase" of new cases in the Aboriginal and Torres Strait Islander community have been confirmed as being under 12 years of age.

Seven new cases of COVID-19 were officially reported in Mildura on Friday, taking the region's active cases to a new record of 16, with five new cases in Dareton. Three further cases were reported in the afternoon.

Ranfurly Primary School in Mildura, as well as Buronga and Dareton public schools, closed until further notice for cleaning and contact tracing after members of the school communities tested positive for COVID-19. Coomealla High School closed on Thursday.

The wearing of masks indoors became compulsory for students in Grade 3 and above in Victoria.

About 100 Aboriginal and Torres Strait Islander community members were tested for COVID-19 on Thursday following concerns the virus was "rapidly spreading" throughout the community.

About 70 people attended an Indigenous-only testing site at Mallee District Aboriginal Services (MDAS), while 30 others were tested using the rapid testing technology.

MDAS Mildura has administered more than 8500 COVID-19 vaccines since the vaccination program began in March, including 324 people who came forward on Thursday.

MDAS chief executive Jacki Turfrey said the number of positive tests from recent rapid testing, which needed to be further confirmed, was higher than official figures released daily by the Victorian Government.

Ms Turfrey said she would not be surprised if official data showed double-digit new cases in the days ahead.

"There is not much messaging in the Mildura community generally about what the trend is starting to look like and what we are seeing, which is an increase, so people are still milling around, no masks, having a good old time with no social distancing," she said.

"There is this false sense of security in the community that everything is OK and we can tick along as normal.

"My concern is that is going to lead us to a Shepparton situation (which has recorded 287 cases and on Friday had 90 active cases)."

Ms Turfrey said she feared the increasing number of COVID cases in children would continue to rise because they are unable to be vaccinated and a lack of accommodation options for those needing to self-isolate.

"The only way we can protect our young ones is for parents and other adults who are in contact with the little ones to get vaccinated," she said.

"There are many households where we have got multiple adult families living under one roof with all of their children.

"Our younger ones can get very, very sick very, very quickly and then I'm concerned about the hospital's capacity to manage that if the numbers grow too fast.

"Every extra case we get is critical in terms of the direction we're heading and the numbers are going up, they are not going down, and they are not being contained within discrete little groups that are not impacting other people and they are also not from one source.

"At the moment (cases) are heading in the wrong way."

Three schools close as COVID spreads

THREE Sunraysia primary schools closed on Friday following positive cases in the school communities.

Ranfurly Primary School in Mildura closed until further notice, while students at Buronga and Dareton public schools requested students and staff self-isolate and follow NSW Health advice and protocols.

A statement issued by Buronga Public School said the NSW Department of Education would continue to work closely with NSW Health to ensure the health and safety of all students and staff was maintained.

"The safety and wellbeing of our staff and students is of paramount importance to us at all times," it said.

"As such we will continue to work closely with NSW Health to ensure that all necessary health advice is adhered to.

"While we recognise this will be disruptive and inconvenient for families, it is important that we follow NSW Health advice and take all necessary precautions to minimise the risk of further transmission to support our community."

Far West Local Health District (FWLHD) said the five new cases in Dareton were in isolation and follow-up investigations and contact tracing were continuing.

Dareton residents were urged to limit their movements in the community and FWLHD described widespread COVID-19 testing as "critical".

Anyone experiencing, or who had recently experienced, even mild cold-like symptoms was encouraged to come forward immediately for testing.

The new cases in Dareton prompted FWLHD to move from surveillance testing to a regular testing regime in the area.

Victorian Chief Health Officer Brett Sutton said the government had agreed to introduce mask-wearing indoors for Grade 3 students and above following an increase of cases in regional Victoria.

"We do need to take some safe and appropriate measures to protect the settings that are now opening up in schools," Professor Sutton said.

"There is good evidence to support this decision.

"We really want to have these measures in place early on to keep kids in school and to make sure that they are safe in the school environment."

Prof Sutton said the indoor wearing of masks for school children from Prep to Grade 2 was "strongly recommended" but not mandated.

Meanwhile, Victoria Police said it would scale back its enforcement at the NSW state border "due to updated health advice".

The police presence will gradually reduce over the next few days and, as of Tuesday, the dedicated border operation with more than 300 police would come to an end, police said in a statement.

"After that point, Victoria Police will use its local resources to patrol the border to ensure ongoing compliance with the permit conditions.

"(The) 100 police resources originally earmarked to work at the state border will be redeployed to Operation Guardian to patrol the metro-regional border.

"The remaining 200 resources will return to their original place of work or to assist with COVID-19 enforcement operations."