A man has been arrested after being seen with what was believed to be a gun, police have said.
Police were called at 12.50pm today (Monday 29) to Alexandra Road and a man was arrested in nearby Eastgate Square.
A 36-year-old man has been arrested on suspicion of possession of a firearm with intent to cause fear of violence. He remains in custody.
Chief Inspector Kris Ottery said: "We have officers out on patrol in Chichester and if anyone has any concerns please speak to us."
Any witnesses are asked to contact police on 101 or online quoting serial 475 of 29/10.