The discovery of five mutilated kittens found dumped in Melbourne's east has sparked fears the disturbed animal killer could soon commit even more disturbing crimes.

Police say the kittens were only a couple of weeks old when someone repeatedly stabbed them, causing gruesome injuries, before being discarded to die slowly and painfully.

A passer-by noticed the dead cats behind a building in Canterbury Road, Blackburn South on March 19 and called a local vet, who called in the RSPCA and police.

Constable Libby Harris said the killings were incredibly disturbing, especially because police realised such an attack on defenseless animals could be a warning sign.

"It's shocking to think anyone would want to harm any animal in that way, let alone five tiny kittens," she said.

"It's also a concern as we know people prepared to kill or injure animals in this way may also be prepared to commit further offences."

In January, a decapitated cat was found on the front lawn of a home in The Basin, about 15km away from where the five kittens were discarded.

Police do not believe the incidents could be linked.

RSPCA Victoria Inspectorate Manager Allie Jalbert said there have been an alarming number of animal cruelty cases so far this year.

"This horrific example of animal cruelty is sadly not an isolated incident," she said.