A horse was doused in petrol and set on fire in broad daylight.
The incident occurred in a green area close to the Red Luas line in Tallaght yesterday.
The horse died from the horrific injuries and a full garda investigation is underway.
The DSPCA said it was one of the “most horrific incidents” their inspectors had ever witnessed.
Five other horses that were in the area where the alleged incident took place and have since been moved to other locations by local authority staff and gardai.
Gillian Bird, CEO of the DSPCA, said they are extremely concerned by the “sinister development”.
“The horrendous death that this horse endured is unimaginable.
“Whilst we encounter many horrific cruelty and neglect cases with regard to abandoned horses, we have never seen such levels of deliberate and depraved cruelty.
“This awful incident only reinforces the plight of abandoned horses that are roaming across the Dublin landscape.
“We are asking all the local authorities to take immediate steps to put a stop to this barbaric behaviour with the removal of abandoned horses to safekeeping,” she said.
The horrific attack occurred in north Tallaght – between the Tallaght and Citywest luas stops.
A “number of young people” are believed to have been involved, and the DSPCA is urging a key witness to come forward.
Some five other horses have been removed “for their safety”, according to the DSPCA.
Gillian Bird from the DSPCA said: “We got a report from the guards and we went out with them this morning to investigate and we found the burnt carcass of a horse. It occurred last night.
Ms Bird said this incident is the “tip of the iceberg” in relation to the kinds of animal cruelty that have been happening.
“There’s a mix of neglect and deliberate cruelty at the moment.”
“We’re asking people to be diligent. If you have a pet, please look after it.”
The DSPCA says the legislation is “already in place” to deal with abandoned and stray horses, and this legislation needs to be enforced.