Five people were killed when a helicopter crashed at a remote airfield inland Sarawak on the northwest coast of the island of Borneo, Malaysian authorities said Wednesday.

The BO-105 helicopter operated by the country's Flying Doctor Service, went down on Tuesday afternoon about 315 kilometres (195 miles) southeast of the city of Miri, disaster management officials said.

"All five on board are deceased as confirmed by reports from the Fire and Rescue Department (Bomba) and the Ministry of Health," Galong Luang, Miri's disaster management chairman, said in a statement.

The pilot, a doctor, a medical assistant and two nurses were among those killed, according to local media.

Footage of the crash on social media showed the helicopter belching smoke shortly before crashing.

A Malaysian air crash investigation team is expected to reach the crash site on Wednesday, the Civil Aviation Authority of Malaysia said. It is unclear what caused the crash at this stage.

Malaysia's Flying Doctor Service assists indigenous communities who are heavily reliant on air transport due to dense jungles and difficult terrain in the country's interior regions.

Teams typically comprising a medical officer, assistant medical officer, nurses and other health staff travel by helicopter or small aircraft on scheduled monthly or monthly rotations to villages and longhouses.