Rugeley Cats Society shared the urgent message after a member of the public approached the charity to tell them two cats had been killed.
They also said that another cat had been set on fire, and that youths had been spotted viciously kicking multiple felines.
A spokesman for the charity said: "We have had a report from a member of the public which is extremely distressing.
"Two cats have been deliberately killed by a person setting his dog on them.
"And one cat has been set on fire and has severe burns to her abdomen and back legs and is now at a vets.
"There is also reportedly a group of youths kicking cats in the head.
"Please keep your cats in. To say this has upset us all deeply is an understatement."
The society said this took place in the WV12 area of Willenhall.
Hundreds of comments were left on a post sharing the information on the Cat Society's Facebook page – with many expressing their anger and sadness at what happened.
The incidents have been reported. Anyone who sees anything suspicious is urged to contact the RSPCA mainline number anonymously on 0300 1234 999.