A stone tile in coded letters dating back since 5,000 BC was made public for the first time on Thursday.

Prominent archaeologist Professor Nikolay Ovcharov held a special news conference in Sofia to show the finding reportedly unearthed 20 years ago.

The tile has sizes 7cm x 8cm x 1.5cm and was previously in private hands, Ovcharov told media.

The coded tile consists of five separate parts with two elements each depicting a human figure with a lifted arm, Ovcharov explained.

The archaeologist has concluded that there is no obvious order in the arrangement of the parts but, definitely, the unique symbols have some meaning.

The find is only the third of its kind dating to that epoch, discovered in Bulgaria, Ovcharov stated. He reminded the pictograms on the two previously found tiles - from Gradeshnitsa and Karanovo - consist of lines only. The symbols on all three are a prototype script, the expert added.

Though Nikolay Ovcharov did not reveal the location of the finding, the artifact apparently comes from the same age as the Mesopotamia civilization. A few months ago a US-residing linguist of Bulgarian origin, Dr Stefan Guide, claimed in Sofia he had decoded these - in his words - Thracian letters.

So far, the science does not know a system of letters that have been used by the Thracian civilisation.

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