Police have launched a critical incident investigation after two men – including a police officer – were serious injured in a motorcycle crash at Mandalong.

Emergency services were called to Mandalong Road near Deaves Road at about 4.40pm on Monday to reports of a crash involving two motorcycles.

A 36-year-old on-duty senior constable, who was riding a marked Police Force motorcycle, suffered serious injuries and was taken to the John Hunter Hospital in a serious but stable condition.

A 69-year-old man who was riding to the other motorcycle, was airlifted to the Royal North Shore Hospital in a stable condition with serious injuries.

A Crime Scene has been set up and officers from the Tuggerah Lakes Police District  are investigating the circumstances leading up to the incident.

A Police motorcyclist and another motorbike rider have been seriously injured in a crash at Mandalong