Kostajnica (Костајница) is a town and municipality in Republika Srpska, Bosnia and Herzegovina. It was also known as Srpska Kostajnica and Bosanska Kostajnica, and was created from part of the pre-war municipality of Bosanski Novi (today Novi Grad). Official language Serbian, Bosnian and Croatian Official script Cyrillic alphabet, Latin alphabet Capital de jure Sarajevo de facto Banja Luka Area â Total â % water 24,811 km² n/a Population â Total (2005) â Density 1,411,000 60/km² Ethnic groups (2005 est. ... ... Bosanski Novi, is a town and municipality in northwestern Bosnia and Herzegovina. ...