An eight-year-old boy was killed in a rollover on the Arnhem Highway overnight, NT Police said.

Police director of communications Mark Wilton said that about 9pm Sunday police received a report a vehicle had rolled on the Arnhem Highway, about 40km outbound from the Marrakai turnoff.

He said the vehicle was carrying a 32-year-old male driver, a 14-year-old girl, and the 8-year-old boy.

“The eight-year-old male was declared deceased at the scene, with the 32-year-old man and 14-year-old female conveyed to Royal Darwin Hospital via CareFlight,” Mr Wilton said.

“Both currently remain in stable conditions. It is believed the occupants are all family members.”

Mr Wilton said the Major Crash Investigation Unit was investigating, and police expected there to be delays on the highway until midday today.

There have been 22 people killed on Territory roads this year, compared to 26 at the same time last year.

Police are asking anyone with information on the crash to call them on 131 444 (quote reference number P25181329).