The Northern Territory has detected 19 new COVID-19 infections as another mystery case is found in Darwin.

Authorities have warned Territorians heath restrictions to slow the virus spreading will be rolled out in the coming days.

A nine-year-old girl was diagnosed overnight, with 18 close contacts currently identified.

“We’re yet to establish how she has tested positive,” Health Minister Natasha Fyles told reporters on Wednesday.

“She has attended a number of locations over the Christmas period.”

Multiple exposure sites are expected.

“I know Territorians are learning to live with COVID in the community, and it can appear to be frightening, but we have a highly vaccinated community,” Ms Fyles said.

“We expected COVID to come. It is here”.

Eight of the other cases are linked to interstate travellers, and three new infections were diagnosed among recent arrivals.

Three cases are linked to the Katherine cluster and all were isolating when they tested positive.

Two new cases were detected among international flight crews, and three cases are under investigation.

Two of these are from a household where a recent arrival to the NT lives but that person has not tested positive for the virus, Ms Fyles said.

Twenty people are in hospital due to COVID-19 but only four are in a serious condition and none are in intensive care.

Most of the cases are of the Omicron variant of the virus.

Chief Health Officer Hugh Heggie warned Territorians a face-mask mandate for some public places was likely to be implemented in the coming days.

The NT has not adjusted its policy requiring travellers to have a PCR test before arriving in the NT.

“I make no apologies,” Dr Heggie said.

“We have a younger population and we’ve got to get young people vaccinated because they can transmit the virus.”

A lockout in Tennant Creek will lift as planned at 5pm on Wednesday.

Meanwhile, the NT government has opened a new all-weather COVID-19 testing facility to help deal with virus surges through the wet season.

The large warehouse in the East Arm industrial area, 15km south of Darwin, opens on Thursday for drive-in and walk-in testing.

– AAP