The Northern Territory has recorded eight new COVID-19 cases, with five infections diagnosed in a remote Indigenous community, including a three-week-old girl.
"They are all Aboriginal Territorians," Chief Minister Michael Gunner told reporters on Wednesday.
"I fear (the virus) will take lives in the territory before the year is out."
The five new infections at the remote community of Robinson River, 1000km southeast of Darwin, are all household contacts.
It brings the total number of cases in the community of about 350 to six.
They include a 13-year-old girl and a 21-year-old woman, along with the baby girl. Two men aged 23 and 29 are also infected.
"We have clear transmission in Robinson River, it's what we were concerned about, it's what we feared," Acting Chief Health Officer Charles Pain said.
The new Katherine cases are two women, aged 21 and 38, and a 36-year-old man, who are close contacts of the other 10 cases diagnosed in the town.
All the new cases are either at or being moved to the Centre for National Resilience to quarantine, with 234 close contacts identified.
"The situation in Robinson River and Katherine is serious," Mr Gunner said.
"We know how quickly Delta can spread within households and we can't be sure yet that it hasn't spread further into the (two) communities or wider in the territory."
Anybody who visited or left Katherine since November 7 and Robinson River since November 11 has been told to get tested as health authorities try to get on top of the outbreak.
Mr Gunner said it was likely but not confirmed that the cluster was linked to the NT's first community transmission outbreak, which was triggered several weeks ago by a woman who unlawfully travelled to the NT from Cairns after visiting Victoria.
Genomic testing results are expected on Thursday.
The latest outbreak in the Top End started on Monday when a 30-year-old woman and a 43-year-old man from Katherine were reported as infected.
The woman is the sister of federal Senator Malarndirri McCarthy.
She is also unvaccinated and had travelled from Katherine to Robinson River where she was diagnosed with the virus, the first case reported in a remote NT Aboriginal community.
Senator McCarthy on Wednesday said she had spoken to some of her cousins in Katherine and they were all double vaccinated.
"There was definitely no hesitancy (about getting the vaccine)," she told the ABC.
But more needed to be done to counter negative attitudes towards getting the jab, the senator added, pointing to messaging in First Nations languages.
Overcrowded housing and low vaccination rates trouble many Indigenous communities across the NT, with reports some homes in Robinson River have 20 occupants.
Health workers have so far tested 138 people in the community with just five positive results returned.
About 77 per cent of Robinson River's residents are fully vaccinated and 87 per cent have had their first jab, with an ongoing vaccination blitz expected to lift rates further.
Health teams have also been sent to Katherine and the communities surrounding it and Robinson River for a testing and vaccine blitz.
Dr Pain said vaccination rates need to increase to stop the health system from being overwhelmed.
"We've been planning for this for a very long time, but I do acknowledge that we are under pressure already," he said.
"We have high demands on our health system in the territory."
The previously diagnosed cases in Katherine include a 71-year-old man, five-year-old twin girls, and a 65-year-old woman who was admitted to Royal Darwin Hospital.
Four women - aged 62, 40, 38 and 22 - also tested positive, along with a 16-year-old girl.
All are household contacts and Indigenous Territorians.
One of the group is a tutor at a primary school in Katherine, which has been listed as an exposure site with three close contacts identified so far.
Homeless people in the town have been offered hotel rooms or other accommodation.
Greater Katherine and Robinson River were plunged into a three-day lockdown on Monday evening.
That has since been extended in Katherine until Monday, with a territory-wide order to wear face masks in most public areas.
