Two little penguins from the famous St Kilda colony have been brutalised and left for dead in separate violent attacks in the past fortnight, volunteers say.

A penguin with a bloody face and chest was discovered inside the fence meant to protect the colony around St Kilda Pier, about 1.30am on Good Friday, by a volunteer.

A penguin at the end of St Kilda pier. Credit:Joe Armao

It follows an attack a fortnight ago where German tourists saw a young man kick a penguin repeatedly, also inside the fence. The penguin's dead body was found soon after and reported to police.

Volunteer Ivan Leong, who was at St Kilda Pier on both occasions, said he confronted a group of about five young men early on Friday morning and asked them to leave the colony in peace.