The Air North plane had taken off from Darwin airport and then crashed at the nearby RAAF base about 10.20am (CST), police said.

Police said it was believed two pilots and two other people were on board.

Paramedics at the scene could not get near the aircraft until the flames had been extinguished.

The cause of the crash is unknown.

Police are notifying the next of kin of the two who died.

Greater Darwin Assistant Police Commissioner Mark Payne told reporters in Darwin that the two people killed were believed to have been experienced pilots who were undergoing routine ongoing training at the time of the crash.

"Our heartfelt condolences go out to the families," he said.

He said most of Darwin would have been able to see the plume of smoke that was generated by the combustion of the aircraft fuel.

"There is always the concern [of a secondary explosion] but it was well attended to very quickly by both airport firies and the Northern Territory Fire Service."

He said both people died at the scene. It was not known where they were flying to nor was the cause of death known at this stage.

"I don't know how hard it went to ground.

"It's a terrible thing to have occurred and the Northern Territory Police will be providing a full report to the coroner to determine what occurred here today."

A spokesman for Air Services Australia in Canberra said the incident involved an Embraer 120 aircraft, a Brazilian-made twin-engined commuter airliner used by a number of Australian regional airlines.

"There was an aircraft crash at Darwin this morning. That incident is continuing," he said.

"We don’t believe there were any passengers on board, which is good news."

Air Services aviation rescue and fire personnel were on the scene, assisted by Northern Territory emergency services.

SMH with wires