By Alvise ‌Armellini

ROME, Dec 12 (Reuters) - Italian authorities said on Friday they had arrested 34 "tomb raiders" ‍suspected of ‌looting treasures from archaeological sites in Sicily and the neighbouring region of Calabria.

The looting of ⁠Italy's rich artistic and archaeological heritage is ‌a centuries-old problem, but the Carabinieri police art squad has had some success in recent years in recovering stolen artefacts.

In Sicily, nine people were placed in pre-trial detention and 14 under house arrest on ⁠charges including criminal conspiracy, theft of cultural property, trading in stolen goods and counterfeiting, police and prosecutors said.

Officers seized ​around 10,000 archaeological artefacts, including 7,000 coins issued by various ‌Greek city states that existed on Sicily ⁠in ancient times, the Catania prosecutors' office said in a statement.

Police also seized hundreds of clay and terracotta vases, bronze rings, brooches and arrowheads. The estimated total value of ​the recovered goods is 17 million euros ($20 million), prosecutors said. 

The word "tombaroli", or tomb raiders, is applied in Italy to criminals who loot any archaeological treasures, not only those found in ancient tombs or graves.

Authorities also discovered a clandestine lab in the eastern Sicilian province of ​Catania, ‍which produced fake ancient coins, pottery ​and copper, and seized some looted coins in Germany, where they had been smuggled for resale. 

AGRICULTURAL CODE WORDS 

In Calabria, two people were put in pre-trial detention and nine under house arrest on similar charges. Prosecutors from the town of Catanzaro said the suspects had operated with the "implicit consent" of a local Ndrangheta mafia clan.

The suspects kept phone contacts to a minimum ⁠for fear of being wiretapped, and used agricultural code words in their conversations, such as "asparagus" or "fennel", to disguise their illicit activities, prosecutors said.

In ​the suspects' lingo, "chainsaw" stood for "metal detector", they added. 

Sicily is home to various ancient Roman and Greek archaeological sites, including the spectacular Valley of the Temples in Agrigento. Calabria also has a rich historical heritage.    

"We are talking about territories as vast ‌as the cultural heritage that lies under their ground," General Antonio Petti, head of the Carabinieri art squad, told a press conference in Rome. 

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(Reporting by Alvise Armellini, editing by)