The discovery highlights a pagan practice common in some villages until a century ago, historians said, where people considered evil had their hearts impaled after death for fear they would return to feast on human blood.
Bulgaria has around 100 known "vampire skeleton" burials, with the two latest specimens, dating back to the Middle Ages, discovered in the Black Sea town of Sozopol, the BBC reported Wednesday.
"These skeletons stabbed with rods illustrate a practice which was common in some Bulgarian villages up until the first decade of the 20th Century," Bozhidar Dimitrov of the National History Museum in Sofia said.
People believed the rod would pin the dead into their graves to prevent them from rising at midnight and terrorizing the living, he said.
Similar sites have been unearthed in other Balkan countries, and vampire legends figure prominently in the region's folklore, inspiring Bram Stoker's gothic horror novel "Dracula."