Katherine is heading into a snap lockdown from noon today for 72 hours after a man who has tested positive to COVID-19 visited the town
Darwin and Palmerston are also being locked down as Territory Chief Minister Michael Gunner said there was a "very real risk" the virus could have travelled into the community.
"For people of Katherine I know this is new and scary for you," Mr Gunner said. "I know that you will be brilliant as we smash this thing."
The case is a man in his 30s, who was released from hotel quarantine in Sydney and travelled to the Territory via Canberra airport, arriving in Darwin late on August 12.
He visited several places in Darwin and then drove a hire-car to Katherine for work, where he stayed at the Notts Crossing Resort and visited the Woolworths.
Subsequent mandatory COVID-19 testing for new arrivals came back positive.
Chief Minister Michael Gunner said the man, who is asymptomatic, has been moved to Howard Springs for quarantine
People will only be allowed to leave home for five reasons, with shopping being confined to click-and-collect services.
School buses will run at 2.30pm if parents cannot collect children before then.