The photographer was situated in the corner where the majority of Croatian fans were sitting during Thursday's match and said he heard monkey noises being directed at the Italy striker.
At one point, he also saw a steward picking up a banana that had been thrown onto the pitch.
European football's governing body made no immediate comment and said only that they were awaiting the report from English referee Howard Webb from the match.
A spokesman for the Italian football federation meanwhile said that neither Balotelli nor any other player had mentioned either being abused or the throwing of a banana.
The official, however, said the federation was unhappy about booing during the national anthem.
UEFA has said it was investigating claims Balotelli, who is of Ghanaian origin, was racially abused during Italy's 1-1 draw with Spain in Gdansk Sunday as well as similar allegations involving Russian fans and Czech player Theodor Gebre Selassie.
Selassie is of Ethiopian origin.
Italy coach Cesare Prandelli, though, had strongly rejected the claims in a number of British newspapers that Balotelli was subject to racist taunts against Spain.
"That's absolutely untrue," the Azzurri coach said at a news conference on Monday.
Manchester City forward Balotelli, 21, has previously said that he would walk off the pitch if he were racially abused by fans.
UEFA president Michel Platini said at a pre-tournament news conference in Warsaw that if Balotelli did that, he would receive a yellow card, advising him instead to alert the match referee, who can now stop matches in the event of racist abuse.
Although UEFA has said it has opened an inquiry into the claims against Balotelli and Gebre Selassie, it has not started any formal disciplinary proceedings.
Racism has become a major issue for tournament co-hosts Poland and Ukraine after claims that far-right extremist gangs were rife at football grounds in both countries.
Warsaw and particularly Kiev have strongly denied the allegations, with both they and UEFA maintaining that racism is a problem across European society and not just at football grounds in the two eastern European countries.
Croatia are already facing possible sanction after their fans lit flares and let off smoke bombs to celebrate two first-half goals in their opening Euro 2012 match against the Republic of Ireland, also held in Poznan, UEFA said on Tuesday.
Smoke bombs were also thrown during the Italy match, AFP reporters and photographers in the ground said.