Police have evacuated a number of buildings after reports of a grenade being found at a property.
Sussex Police were called at 9.35am by residents concerned about a a possible WWII-type grenade at a property in Lansdowne Road.
It is currently unconfirmed whether the device is live or not and police are awaiting Explosive Ordinance Disposal to assess the item.
A spokesman for Sussex Police said the A259 had to be closed as a precaution.
A tweet from Arun Police said: "Currently dealing with a WW2 device near Lansdowne Road Littlehampton, we aim to have the A259 open asap. #CR371 #EsectionArun
More information on this to follow.