After the match ended, a composed Tomic apologised for his distasteful comments but claimed that he was provoked by the heckler, who said "negative stuff" in his mother tongue (Serbian-Croatian).
Tomic has apologised for the incident, suggesting his Croatian roots may have been a factor in the clash against his Bosnian opponent.
The reason for that reaction came back in the opening set, when the world number 19 got involved in a highly distasteful altercation with a member of the crowd, shouting at them to "suck my b*lls", and "I will put my b*lls in your mouth". He definitely baited me the whole set for me to say that.
"I just saw he left and the crowd clapped a bit but I have no idea who he is". Big points, I should say. However, the microphone didn't pick up what the heckler had said.
Tomic is no stranger to controversy.
At Wimbledon earlier this summer, Tomic was forced to apologise for using the word "retard" in a press conference.
Tomic added: "I'd like to see what the microphone picked up (of) what he said".
Tomic drew heavy criticism in May following his exit from the Madrid Open when, on match point against Fabio Fognini, he held the racquet by the strings and did not offer a shot to the Italian's serve.
In July past year, he was arrested in Miami after a wild party in a hotel penthouse suite.
Tomic, seeded 17 for the tournament, committed 78 unforced errors in his tame defeat to Dzumhur who goes on to face either Illya Marchenko of Ukraine or Croatia's Ivan Dodig. "It's tough", Tomic said.