The Northern Territory has detected eight new COVID-19 infections, as a long-running outbreak forces the lockdown of Tennant Creek.

Four new cases were diagnosed in the remote town, 990 kilometres south of Darwin, Acting-Chief Minister Nicole Manison said on Friday.

“This is a serious situation. Tennant Creek is a major transit centre. There is a vast amount of movement,” she said.

“We have already launched a major public health response”.

The new cases include an unvaccinated woman in her 40s who was infectious at a town camp for six days.

Two women in their 40s and 20s and a child are also infected.

Ms Manison said the timing was “complicated” due to the high number of people moving through the town of 3500 on Christmas school holiday travel.

About 80 per cent of residents have had one vaccination dose and 70 per cent are fully vaccinated.

“This is frustratingly low. Disappointingly low,” Ms Manison said.

The town was locked down until 5pm Monday, and the entire Barkley local government area was ordered to wear face masks.

Anyone who was in and left the town within the last seven days has been ordered to isolated and get tested.

A woman in her 30s and a teenage boy from Katherine’s east, 320 kilometres south of Darwin, also tested positive for the virus.

The pair were quarantined at The Centre of National Resilience at Howard Springs, south of Darwin.

It brings the current outbreak to 100 cases with more expected.

It started when an infected woman illegally entered the NT in late October.

The 21-year-old was fined for lying on her border entry form as the virus spread from Darwin to Katherine and three Aboriginal communities.

Police have since launched a fresh investigation into the border breach after an Aboriginal woman died from COVID-19 in early December.

A lockout was declared in Timber Creek and the nearby community of Gilwi late on Tuesday.

A lockout in Kalkarindji, 550 kilometres south of Darwin, and Timber Creek, 225 kilometres east of Kununurra in Western Australia, will end at 2pm Friday. However, masks must be worn until 5pm Monday.

People in Katherine and its surrounding communities have also been ordered to wear masks.

Meanwhile, two fully vaccinated men in their 20s in Yulara, 450 kilometres southwest of Alice Springs, have been diagnosed with COVID-19.

The pair had travelled from Brisbane where they came into contact with the virus.

Authorities are contacting passengers on flight Jetstar flight JQ667.

-AAP