Police are trying to establish the identity of a body found on fire on a dirt road by a passing motorist in northern NSW.

The body was discovered on a dirt road near Tweed Heads at Dulguigan.

Police said they were called to an isolated road just before 7:30am, when a passing motorist spotted what they thought was a burning log on the road.

The driver pulled over and discovered it was a human body on fire.

A crime scene was established and officers are investigating the circumstances around the death, which is being treated as suspicious.

Police are trying to establish the gender and identity of the body and are appealing to anyone who saw unusual activity in the area, or who has concerns for a missing friend or family member, to contact Crime Stoppers.