Mileks acquired the shares on May 27, it said in a bourse filing.
The shares were acquired for 873,677 marka ($484,605/446,704 euro), at a price of 1,382 marka per share, in a block deal, Banja Luka Stock Exchange (BLSE) data shows.
Drina Osiguranje's shares have not traded on the BLSE in the past year.
(1 euro = 1.956 marka)