Thieves have stolen a sixth-century BC bronze ornamental stud from Pompeii, the Special Superintendency for the Archaeological Heritage of Naples and Pompeii said on Thursday.
"This theft is a wound to Pompeii and to Italy's Cultural Heritage, said the director of the 2,000-year-old site, Massimo Osanna.
"Although it is not a priceless artefact, it affects me personally as it came from an area I have excavated," Osanna said.
The ancient door stud, measuring 7.3cm in diameter had been on display at the UNESCO World Heritage site's 'Pompeii and the Greeks' exhibition and was on loan from the city of Potenza's archaeological museum.
The stud was one of four on exhibit at the show, the archaeological superintendency statement said.
It was of "moderate value", said Potenza's archaeological museum director, Marta Ragozzino.
The stud, like the other three on display, was screwed onto a panel and covered by a transparent protective layer, Osanna stated.
The building housing the exhibition is monitored by staff from a security firm during the day and by video-surveillance equipment at night, Osanna said.
Police have closed the entire exhibition area to investigate the theft, which they believe occurred on Wednesday evening, possibly when the exhibition was open.