Animal welfare groups have condemned a series of violent attacks on penguins at a popular Melbourne tourist spot.



The RSPCA says the incidents, in which one of the St Kilda Pier colony birds was killed, reflects an alarming trend in acts of cruelty.



Only kilometres from Melbourne's CBD, St Kilda's population of penguins has thrived in recent years.



Their suburban home has become a drawcard for locals and tourists alike.



But the birds have also attracted some unwelcome sadistic attention.



Two nights ago, local wildlife volunteer Ivan Leong witnessed a group of youths causing trouble on the pier.



"They were climbing all over the rocks, harassing, chasing the penguins and touching them," he said



Shortly after one of the birds was seen battered and bloodied with what looked like severe cuts around its eye and mouth.



It follows another incident a fortnight ago in which a bird was kicked to death by a youth.



Earth care St Kilda volunteer, Mr Terry Lobert, said it was a sickening and horrifying attack. "I just can't imagine what goes through people's heads that they want to kick a little, cute defenceless penguin."



Authorities are now looking at ways of better protecting the penguins, while at the same time allowing the public to enjoy the rare experience of a marine wildlife colony so close to a city centre.



According to Chris Hardman, from Parks Victoria, numbers have swelled from a hundred to more than a thousand in recent years. "We think there are a range of things we could do over time. We could improve some fencing. We could create some separation."



RSPCA inspector Michelle Green said these weren't isolated acts of cruelty, with drug and alcohol use often a contributing factor.



"Violence against animals is certainly becoming more prevalent in society these days," she said.



And there's a warning for those cowardly penguin attackers.



While the birds may look cute and defenceless, penguin expert Zoe Hogg said they possessed hidden strengths.



"If you try and approach them they have got a very, very strong beak and it has a hook on the end and if they grab hold of you they twist the skin and you get a nasty big bruise," she said.



Not to mention possible jail time and a hefty fine for interfering with wildlife.