ARCHAEOLOGISTS say they have discovered a 4,500-year-old ceremonial centre, the oldest ritual site in Greece.

Excavations resumed for a few weeks this summer at Dhaskalio Kavos - Kavos for short - on the tiny island of Keros, after a lull of nearly 20 years. The problem with the site had been that it was disturbed by looters, who made a lucrative trade in the 1960s of the now famous minimalist Cycladic figurines. As a result, archaeologists could never be sure whether fragments of the Cycladic statuettes had been smashed in antiquity or more recently by smugglers.

That puzzle has now been solved by this year's excavation on an undisturbed patch of the site dating to 2,500BC.

"All the material found was already broken in fragments before it became buried in ancient times. Moreover, the rarity of joining pieces (as well as the different degree of weathering of the fragments) makes clear that they were broken elsewhere and that they were brought, already in fragmentary form," says an announcement from the team of Greek and British archaeologists who head the dig.

The puzzle of the broken fragments has come to be known as the "Keros enigma".

The materials come from as far away as Naxos, Amorgos, Syros and probably mainland Greece, they say, making Dhaskalio Kavos "the first major ritual centre of Aegean prehistory".

Archaeologists, led by Colin Renfrew of the University of Cambridge, say they were overwhelmed by the sheer volume of finds. "The quantities of such material (fine pottery, marble objects) found at this site rivals the total of the finds excavated from all the known Cycladic cemeteries," the announcement says. They have ruled out the possibility that the site was a cemetery, because teeth would never turn up among the sherds.

They suggest that the rituals may have spanned enormous distances across the Aegean, and taken many days to complete. "The rituals involving breakage may have been initiated elsewhere, with the ritual deposition at Kavos on Keros forming the last phase in a more complex process."

Next summer's excavation is expected to reveal whether there was a sanctuary at Kavos and attempt to find a contemporary settlement on the nearby islet of Dhaskalio. Joining Colin Renfrew on the current dig are Neil Brodie (also from the University of Cambridge), Olga Philaniotou (Greek Archaeological Service) and George Gavalas.