Four people have died in three separate road accidents across WA, including two men in Perth and two people in the far north.

Two people were killed in a crash near Kununurra, in the remote Kimberley.

Four other people, including two children, were also in the car and two were taken to Kununurra Hospital, one in a critical condition.

That patient, a child, is expected to be flown to Darwin by Royal Flying Doctor for further medical treatment.

The adult driver of the vehicle and another child passenger received no injuries.

A passing motorist came across the accident on the Gibb River Road, about 180 kilometres west of Kununurra, just after midnight.

The double fatality happened on the remote Gibb River Road Kimberley. ( ABC News: Erin Parke )

However, the remoteness of the terrain meant emergency services were not able to reach the site — which is outside mobile range — until hours later.

Police said an emergency services doctor staying at a nearby station was able to get to the scene and start helping the passengers in the meantime.

The Gibb River Road is a dirt and gravel four-wheel track, famous for its remote vistas and a yearly mountain bike race.

Emergency services had to travel to nearby Ellenbrae Station in order to communicate information on the crash.

In Perth, a 45-year-old man died after his car hit a tree at a crash in the north-east suburb of Bullsbrook.

Emergency services were called to the accident on Chittering Road shortly after midnight.

The man died at the scene in Bullsbrook, on Perth's eastern outskirts. ( Supplied: Night News )

Police said the man's car appeared to have left the road as in travelled along a bend, and he died at the scene.

Meanwhile, a man died and another person was seriously injured in a separate crash in the Perth suburb of Forrestfield this morning.

The single vehicle crash happened near the intersection of Roe Highway and Berkshire Road.

The highway is closed between Kalamunda Road and Berkshire Road and is expected to remain closed for several hours.