Nine Indigenous Northern Territorians have tested positive for COVID-19 as Senator Malarndirri McCarthy revealed her unvaccinated sister carried the virus into a remote Aboriginal community.
It brings the territory's latest outbreak to 11 cases after the Labor senator's 30-year-old sister and a 43-year-old vaccinated Aboriginal man were reported as infected on Monday.
The new cases are household contacts of the pair, who live in Katherine, about 320km south of Darwin, Chief Minister Michael Gunner says.
"This is a serious escalation of the COVID-19 situation in the NT," he said on Tuesday.
"This is a lot of cases. This is a case in a remote community, These are all Aboriginal Territorians. This makes real every fear that we've had."
The new cases include a 71-year-old man, two five-year-old twin girls and a 65-year-old woman, who has been admitted to Royal Darwin Hospital.
Four women aged 62, 40, 38 and 22 have also been diagnosed with the virus, along with a 16-year-old girl.
All have been moved or are in the process of being moved to the Centre for National Resilience, with the exception of the woman in RDH.
It is not known if the group were vaccinated.
Mr Gunner said it was likely 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.
Contact tracers have identified 161 close contacts, with Deputy Chief Health Officer Charles Pain saying they were in a "desperate race" to track the outbreak down.
"We don't know how far it's spread," he said.
No new cases were diagnosed in the remote Aboriginal community of Robinson River overnight, where Senator McCarthy's sister had travelled and was diagnosed.
However, the results from 20 priority tests won't be available until Wednesday, with plans to test all 350 people in the community.
Senator McCarthy's sister's case is the first COVID-19 infection reported in a remote NT Aboriginal community.
"I'd like to say a personal message and that is that to my sister, who is the source of the COVID infection in Robinson River, our thoughts and prayers are with her and our family," she told reporters.
Health teams have been sent to Robinson River, Katherine and surrounding communities for a testing and vaccine blitz.
Greater Katherine and Robinson River, about 1000km from Darwin, were plunged into a three-day lockdown on Monday evening.
That has now been extended in Katherine until Monday, with a territory-wide order to wear face masks in most public areas.
Mr Gunner warned there could be dozens more cases in the coming days.
He said the virus could have "seeded" and moved to other communities in the NT, and more lockdowns and lockouts were possible.
There are currently some large Indigenous funerals and ceremonies underway in the NT.
Police Commissioner Jamie Chalker called on anti-vaccination protesters to stay home.
"I can't be bothered dealing with your rubbish ... There's just too much at stake," he said.
About 77 per cent of Robinson River's residents are fully vaccinated and 87 per cent have had their first jab, according to NT Health statistics, which have been criticised for being inflated by about 10 per cent.
In Katherine, 64 per cent of the 6000 residents are fully vaccinated and 78 per cent have had their first dose, NT Health says.
Across the NT, 52 per cent of Indigenous Territorians are double-dosed and 72 per cent have received their jab, according to commonwealth data.
About 30 per cent of the NT's 246,500-strong population are Indigenous.