The carvings point to South Eastern Weurope, and since I know that the bards of the Balkans use a one stringed instrument to accompany their songs and epics I looked up Gusla (serbocroat. gusle).

Library of Congress Subject Headings:
Gusle
   UF Gusla
   BT Musical instruments--Balkan Peninsula
       Stringed instruments, Bowed

The Brockhaus (THE German lexicon publisher) Musical lexicon has a small sketch of the instrument with its typical horsehead. It is described as onestringed, bow operated, with coat covered corpus.
The string is pressed not on the board but from the side, often generating flageolets.