The tournament will be played in the Novinarski Dom building, the head office of the Croatian Journalists' Association, until July 8 and will feature 12 grandmasters. It will be the first time a current world championship, Magnus Carlsen of Norway, plays in Croatia. The tournament prize fund is $325,000.
Among the participants will be former world champion Viswanathan Anand of India (9th on the FIDE list), an absolute world champion from 2007 to 2013 who lost the title to Carlsen, and American Fabiano Caruana (2nd on the FIDE list), who challenged Carlsen last year, but lost.
The tournament is sponsored by the Croatian government, and in his opening remarks Prime Minister Andrej Plenkovic said: "In the days ahead Zagreb will be the world capital of chess. I hope this tournament has a positive effect on young people and I thank Garry Kasparov for helping ensure that it is held in Zagreb."
Kasparov, a world championship from 1985 to 2000 and one of the best chess players of all time, also attended the opening ceremony. He was granted Croatian citizenship in 2014.
Among those attending were Science and Education Minister Blazenka Divjak, Culture Minister Nina Obuljen Korzinek and Tourism Minister Gari Cappelli.
The tournament opened with Prime Minister Plenkovic making the symbolic first move against Carlsen.