The group reported that the horse, named Birillo, was killed in the Italian city on November 18 when he was hit by a truck.
"He lay dying for three hours and it is not known why he was not removed to a vet," the coalition said.
It also noted that last spring, Rome activists petitioned the government to ban the horse-drawn carriage industry in the city. "We are working with activists in Rome and other cities to call attention to the cruel and inhumane carriage trade on an international level," the coalition said.
When last available online, a poll on la Repubblica showed that 73% of respondents voted to ban the industry.
A public hearing on legislation to ban the operation of the horse drawn cab industry in New York City is scheduled for December.