A 28-year-old man is in hospital with serious injuries after a stabbing in Hove.
Sussex Police were called to Harmsworth Crescent shortly after 5.30am and found the man in the street bleeding profusely from his injuries.
Officers said it was believed stabbed and police are urgently trying to find the weapon.
A 32-year-old man has been arrested and is being questioned in custody.
Det Chief Inspector John Wallace said the injured man was taken to the Royal Sussex County Hospital and has undergone surgery.
He said: "This is a very serious assault and we are carrying out detailed inquiries to establish exactly what has happened."
Scenes-of-crime officers were carrying out forensic examinations in Harmsworth Crescent on Saturday.
Anyone who saw what happened is asked to contact the force.
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