For centuries, residents of Guardia Sanframondi have marked the Feast of the Assumption of the Virgin Mary with a procession behind her statue through its medieval byways.

Such acts of devotion to the mother of Jesus are common — but not the way it is done in Guardia, which has 5,700 residents and lies one-and-a-half hours northeast of Naples. There, the procession is marked by flagellation, an act of flesh-and-blood penance. The observance is one of the few well-known examples of its kind in Europe, though the practice is more common in Latin America and the Philippines.

Some participants — flagellanti — strike their backs with small strips of metal chained together. Others — battenti — tap against their bare chests with disks of cork pierced by needles, creating red patches of raw flesh, and sometimes blood. (The needles number 33, the age of Jesus at his death.) Attendants pour white wine on the cork as disinfectant, and to keep the wounds open.

Roberto Boccaccino

The penitents wear white hoods and robes to protect their anonymity, keeping their identity secret even from family members in what many see as a highly personal spiritual experience.

The procession takes place every seven years. Each of Guardia’s four main neighborhoods organizes its own procession, which begins on the Monday after Aug. 15, the feast day. The participants join together on the following Sunday for the main procession, when the flagellation occurs.

In pictures from the event this summer, Roberto Boccaccino captured the flagellants at various moments: adjusting one another’s hoods, gathering in the square before the procession, in midflagellation, resting together afterward. He showed children dressed up as various biblical figures, and the faces of the observers. Mr. Boccaccino gained access to the penitents’ homes after getting to know them during the week and explaining that he would protect their anonymity, show respect for their spiritual mission and tell the whole story.

Roberto Boccaccino

Mr. Boccaccino, 26, is a native of nearby Benevento and is a freelancer who ranges across Europe. In an e-mail exchange, he said he was struck by how an entire town could be involved in something so not of the modern world.

“The hoods, the pain and the corporal punishment as reconciliation with God — everything comes nearly unchanged from the Middle Ages,” he said.

The ritual has drawn some criticism over the years. Recently, suggestions have been raised that members of the local crime organization, the Camorra, use the anonymity as a way of seeking secret redemption, Mr. Boccaccino said. But no opposition was apparent during the procession.

“We are talking about something absolutely personal and intimate,” the photographer said. “They don’t hurt anyone but themselves and if you don’t want to see it, simply don’t go there.”