Croatian police stated that remains may be of Croatian and German soldiers executed by Yugoslav Communists at the end of the World War II. Forensic experts were investigating the site.
"The victims were members of a Croatian army unit captured and executed by Communist Partisans between May 8 and 9, 1945. There are five more other graves in the immediate vicinity contains the remains of at least 50 victims," said Ivica Relkovic, civic action leader and head of the Responsible Croatian Society organisation.
Croatian authorities were still working on a massive grave at Harnica, where an estimated 4,500 bodies of Croatian and German troops from the so called Blue Division were executed and buried in 1945.
Croatia broke off from Yugoslavia in 1941 and sided with Hitler's Germany. Following the victory of Yugoslav communists under Marshall Tito, Yugoslavia's later long-term leader, the country returned to the union under Belgrade's sovereignty.
"The number of mass graves from the era across former Yugoslavia is probably greater than 1,000. There are 600 mass graves in Slovenia, 840 in Croatia and 90 in Bosnia," said Tomislav Karamarko, Interior Minister of Croatia.