The People says after the home side were awarded a last-minute penalty, the French defender stunned team-mates and fans with his antics which included:
Racing across the pitch to kick an advertising hoarding.
Allegedly making a one-fingered gesture at City supporters.
Choking back tears as he staged a three-minute sitdown on the pitch after the final whistle which ended with Wenger leading him off.
However, Wenger insisted that Gallas's reaction was understandable.
"William was frustrated and I can understand that," Wenger said. "He was frustrated because of a last-minute mistake. He did not kick anybody. You can't always have people 100 per cent committed always acting in a fair way. He didn't look at the fans in the stand or fight anybody. Let's be serious."