Owners should make sure their pet is on its dog collar and lead when around horses, a charity has said.
The Blue Cross and the British Horse Society (BHS) have issued this warning after a dog was fatally injured by two horses while out walking.
Horses are also at risk from these encounters. Last month a championship pony from Wiltshire had to be put down after suffering injuries when a loose dog got into its field.
Julie Bedford, head of behaviour at Blue Cross, said: "Clashes between dogs and horses usually happen if the animals are nervous or frightened of each other and can quickly escalate into a very dangerous situation.
"If in doubt, dogs should always be kept on a lead around horses, especially in unfamiliar surroundings."
She added that it is very important that owners know how to control their animals and train them to be calm around other animals from a young age.