Acting Chief Minister Nicole Manison said the decision to enforce a lockdown in the town of Tennant Creek followed a unvaccinated woman, who had been in the town since Sunday, testing positive for the virus.
"This is a serious situation," Ms Manison said.
The woman is one of eight new infections recorded in the territory today.
Six are linked to the Katherine cluster, which now has a total of 100 cases.
The other two cases were found in Yulara, which have been described as low-risk to the community.
Tennant Creek has a COVID-19 vaccination rate of below 70 per cent first dose.
Residents of Tennant Creek only have been told they are only five reasons to leave their home during the lockdown:
- to receive medical case, including getting a COVID-19 test or vaccination
- to purchase groceries and essential supplies
- to undertake essential work that can't be done remotely
- to exercise outdoors for up to one hour within 5km of home
- or to provide care or support to someone else.
Ms Manison said there was no reason for residents to "panic buy", emphasising grocery supplies will not be impacted by the lockdown.
The lockdown is due to be lifted at 5pm on Monday.
Anyone who has left Tennant Creek in the last seven days must get a PCR test and isolate until a negative result is received, Ms Manison has said.
The acting Chief Minister also announced there is a mask mandate in place until 5pm Monday for the entire Barkly LGA.