From 4pm on Tuesday, anyone arriving into the Northern Territory from interstate or overseas will have to self-isolate for 14 days due to strict new border controls.

Chief Minister Michael Gunner announced the new restrictions this afternoon.

"I've seen what's happening overseas, I've seen what's happening down south and I'm not going to let that happen here," he said.

"The Territory comes first."

NT Police Commissioner Jamie Chalker urged tourists heading to the NT to reconsider their plans.

"We ask for cooperation – if you have no necessity to be in the Territory, please reconsider your plans," he said.

Commissioner Chalker said that NT Police and the Government were likely to keep the measures in place until September.

"We are working for this to be in place for about six months," he said.

Mr Gunner said anyone arriving in the Northern Territory from Tuesday will now have to declare at the point of entry that they would isolate for 14 days and let the authorities know where they would be for this period.

"We will have police checkpoints at the border to enforce this requirement," he said.

"We will also have signs on our major roads leading into the Territory so arrivals know exactly what will be required if they enter the Territory.

"And if you can't meet those requirements, then turn around and go home."

Mr Gunner said that the Territory was "probably the safest place in Australia" right now and "we intend to keep it that way".

There are currently five confirmed cases of COVID-19 in the Northern Territory.

The latest two cases involve a couple who had been on the Ruby Princess cruise ship in Sydney before flying to Darwin today.

The new requirements will apply to entrance by road, rail, air and sea.

Exemptions will apply only to health and emergency services, defence and policing, flight crews and freight, though all arrivals will have to show they meet the essential services criteria.

Exemptions may also be granted on compassionate grounds.

Tasmania was the first of Australia's states to introduce tough border measures earlier this week.