Sussex Police cordoned off an area to the west of Brighton Palace Pier.
Part of the beach was closed following the discovery of the item earlier this afternoon at around 2:20pm.
"The scene has been made safe while we await attendance from the Explosive Ordnance Disposal," a police spokesman said just a short while ago.
Members of the public have been advised to stay away from the area until the beach is made safe and reopened. However, it is not known at this time when the beach is likely to re-open.
A section of beach west of Brighton Palace Pier has been cordoned off after an item – possibly an unexploded mortar shell – was found.— Brighton&Hove Police (@BtonHovePolice) April 18, 2021
The scene has been made safe while we await attendance from the Explosive Ordnance Disposal.
Please stay away from the area in the meantime. pic.twitter.com/05LKcPEaIQ