LONDON — The bodies have been dumped on doorsteps with chilling regularity. There was Oscar, an 8-year-old tabby, his head and tail cut off; Oreo, a Siamese kitten left at the bottom of a garden, decapitated and with her collar lying across her body; and Paddy, who had been hacked in half. The missing heads have not been found; they might have been kept as trophies.

The gruesome killings and mutilations of scores of cats in London over the past six months, starting in the South London neighborhood of Croydon, are stoking fears of a dangerous sadist in this city of animal lovers. Several newspapers and broadcasters have taken to calling the killer the Croydon Cat Ripper.

“Because animals cannot report incidents of abuse against them and can do little to fight back, they are the perfect practice victims for violent people,” said Elisa Allen, associate director of the British chapter of People for the Ethical Treatment of Animals, or PETA. “The pain and fear that any of these cats experienced is unimaginable.”

PETA is offering a reward of just over $7,000 for information leading to an arrest.

The pattern of attacks first came to light last fall when South Norwood Animal Rescue and Liberty, a local organization, began to document the cat deaths. Tony Jenkins, who runs the group with his girlfriend, Boudicca Rising, said they had documented 46 cats that they believed had been killed, possibly by the same person or people.