A horse became impaled on a fence after it was thought to have been spooked by fireworks, the RSPCA said.
The injured horse was rescued from a fence post near a hedge at Bryn Celyn, Holywell, Flintshire on Saturday.
RSPCA Cymru inspector Jenny Anderton said it seemed "pretty likely" the horse "was frightened by nearby fireworks".
The animal was rescued from the post after "some time and great difficulty", Insp Anderton added.
"The horse must have been laying there all night and it took us until 13:00 to get him out, get him up and get him on a wagon for the vets to attempt surgery on his very serious wounds, caused by impaling himself on the hedge and fencing," Insp Anderton said.
"We of course don't know for definite, but it seems pretty likely that Harry was frightened by nearby fireworks that were set off."
She urged people to be mindful of animals at this time of year.
"This incident really does show what the effects of fireworks can be," she said.
Local livery owner, Lily Roberts, who helped with the rescue, said: "He had crushed the hedge and we had to cut the hedge around him.
"It was just horrible. I had never seen anything like this before."
A spokeswoman for RSPCA Cymru said Harry was being cared for by vets.
The animal welfare charity is calling for responsible use of fireworks and the adoption of tighter regulations concerning their use as part of their "Bang Out Of Order" campaign.