In his letter, Bandic, who is also honorary president of Dinamo Football Club, recalled that Croatia had adopted legislation on sports fans and that it was being implemented.
"Unfortunately, all the mechanisms and all the rigorous measures we otherwise take in all official and international matches played by our clubs and our national team, failed in this case," Bandic said.
"We thought that this could not happen in a friendly match in a friendly country such as Austria, but we were proved wrong by the events and we will have to draw a lesson from them for the future," he added.