A dog has been hailed as a hero in Japan after she saved the life of a man who was having a heart attack by sounding the alarm with her incessant barking.

Koume, a 5-year-old mongrel, was handed an official letter of appreciation by local fire officials at a special ceremony last month for her valiant work at a horse riding club in Wakaba-ku, Chiba City.

According to the horse riding club, a man in his fifties collapsed at the riding park on February 25. Koume, a usually placid pup, raised the alarm with her barks which then allowed people to rush to the man's aid.

"Koume is usually quiet and barks only under rare circumstances," Yuna Maruo, a 23-year-old riding instructor who took part in saving the man that day, said. "But when an emergency arises, Koume does bark."

The Wakaba Fire Department said life saving treatment can be given to heart attack victims if people are alert to "the slightest change."

"Koume's action in calling for help and the staff's actions were a perfect response," a fire department official said.

According to the club, Koume's barks enabled staff to quickly call an ambulance and paramedics used an automated external defibrillator on the rider just in time.

The man has since returned to riding at the club.

The club said it had employed female canines as their "mascots" to greet members for generations.

According to Maruo, Koume has previously drawn attention to a horse trying to flee the facility by jumping a fence and when another old horse was having difficulties standing on its own.

Koume grew up under the nurturing of another pooch called Ume, who Maruo believes helped teach her how to call for help in the time of a crisis.

Koume's mentor has since passed away, but the riding instructor said: "Ume must be happy in heaven".