People enjoying the sun were evacuated from a stretch of Brighton Beach after a suspected unexploded mortar shell was found.
Police have told people to stay away from the area until a bomb disposal squad arrive.
There is a heavy police presence in the area with at least three police cars and two vans at the scene, Sussex Live reports.
A large cordon has been put in place and people have been removed from the beach.
One witness said: “On Brighton beach and police have evacuated it [because] apparently there’s a bomb threat, just our luck.”
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She added that “easily hundreds” had been evacuated.
Many members of the public are watching from behind the cordon as officers scour the area.
A statement from Brighton and Hove Police said: “A section of beach west of Brighton Palace Pier has been cordoned off after an item – possibly an unexploded mortar shell – was found.
“The scene has been made safe while we await attendance from the Explosive Ordnance Disposal.
“Please stay away from the area in the meantime.”
The Mirror has contacted Sussex Police for additional comment.