Rescuers are on their way to a teenager who has fallen about 80 metres down an escarpment near Lake Macquarie in the New South Wales Hunter region.

Officers say the 17-year-old boy was with a group of people trying to get into a bushland dance party when he slid down the slope at Watagans National Park.

His friends raised the alarm and the boy was spotted earlier this morning.

Due to the rugged terrain and weather conditions, rescue teams have started to walk to his location.

Police believe he may have possible fractures and internal injuries.