A 50-year-old man is in a critical condition in hospital after an alleged altercation in north Belfast.
A man in his 40s has been arrested after the incident in the Brae Hill Park area of Ballysillan and a car has been removed for forensic examination.
Police, who have released few details about what happened, said they received a report of an "altercation" on the street at around 2am.
PSNI Detective Sergeant Kenneth Leckey said: "Detectives are working to establish the circumstances surrounding the incident which has left a 50-year-old man critically ill in hospital.
"Police received a report of an altercation in the street at around 2am, and when officers arrived at the scene discovered a man with head and leg injuries. First aid was administered by officers until the arrival of an ambulance which took the casualty to a nearby hospital. A man in his 40s was arrested at the scene and a car has been taken away for forensic examination."
He urged any witnesses to the "very serious incident" to come forward.