A total of 70 Quran memorizers and reciters from 46 countries are taking part in the competition.
It is being held in the categories of Quran recitation, memorization of the entire Quran and memorization of 15 and five Juzes (parts) of the Holy Book.
Mohammad Khakpour and Hadi Esfidani are representing the Islamic Republic of Iran in the categories of memorization of the entire Quran and recitation, respectively.
Croatia’s top Islamic body, the Islamic Affairs Department, organizes the contest annually.
Sheikh Aziz Alili, the imam of Zagreb Islamic Center, heads the panel of judges.
An exhibition of calligraphy works featuring verses from the Quran has been mounted on the sidelines of the competition, which will wrap up on Saturday.
Croatia is an Eastern European country with a population of around five million.
Islam is the second-largest faith in Croatia after Christianity. The religion is followed by 1.47% of the country's population according to the 2011 census, compared to 91.06% Christians.