Royal Navy divers are on scene dealing with the item – and police have put a cordon in place.
Pictures from the scene show the extent of the disruption.
A message from the Editor, Mark Waldron
You can subscribe here for unlimited access to our online coverage, including Pompey, with 70 per cent fewer adverts for less than 20p a day.
A message from the Editor, Mark Waldron
2 / 2