Italian police have discovered a mob-linked race track where they say horses were pumped full of Viagra and other drugs to fix races.

The illegally built and operated track, known locally as "Miss Charmet," is located on the outskirts of Naples city - home to the Camorra, the local version of the Sicilian Mafia.

"We are able to ascertain the use of the famous (drug) Viagra to increase the performance of these horses," police commander Mario Pantano told local television.

It was not clear how Viagra affected the horses' speed.

According to local media, the track and its horses, worth an estimated five million euros ($6.4 million), were seized by authorities investigating illegal doping of horses.