MADRID – Eighty-one people have been arrested in Spain in an operation against a ring illegally dealing in antiquities looted from archaeological sites.

Thousands of pieces were recovered in the operation, mainly from Roman times, though there was also a quantity of medieval, Islamic and even prehistoric items, police officials said Friday.

Noteworthy among the pieces found during some 115 searches were more than 6,000 Roman and medieval coins, arrowheads, brooches of Roman origin, Visigothic earrings and buckles, polished stone axes, steles with inscriptions in Arabic, columns and votive offerings.

Some of the looted pieces came from the prehistoric sites of Castulo and Los Villares in the southern province of Jaen, and from Calatrava la Vieja in the central region of Ciudad Real, one of the most important Islamic archaeological sites in Spain.

The ring that was broken up operated in several Spanish provinces and had clients in the United States, Britain and Germany.

Police also dismantled in Jaen a sophisticated workshop that skillfully restored and, at times, faked archaeological items that they sold as genuine.

The criminals would copy an original piece with high-precision tools and age it with chemical and physical processes, making it difficult even for experts to determine if it were a genuine antique or a copy.

Afterwards they offered the items on auction Web sites or sold them directly to established customers.

Sometimes, as the chief of the police’s cultural-heritage brigade, Antonio Tenorio, said, the crooks submitted phony bids to drive up the prices of their merchandise on Internet auction sites.

Spanish police connect the dismantled organization’s kingpin with a network that launders money through illegal sales of precious metals such as silver and gold.

Cops have seized more than 120 kilos of gold and silver, 900,000 euros ($1.2 million) in cash, equipment for smelting metal as well as a machine gun and six other firearms.

Meanwhile, around a hundred bank accounts have been frozen in a score of banks, one of them in Switzerland. EFE