Conflicting reports suggest that the death toll could be as high as 75.
The incident occurred in the city of Iskanderiyah, 30 miles south of the Iraqi capital.
"They were just handing the trophy to the winners, the suicide attacker blew himself up in the crowd," a village police captain said.
Among those killed was the mayor of Iskanderiyah.
"The mayor died in hospital as a result of the serious wounds he suffered in the blast," a medic said, speaking on condition of anonymity.
According to the police captain, at least 71 individuals were wounded in the blast.
While no group has yet claimed responsibility for the attack, but the terrorist group Daesh, also known as IS/Islamic State, is active in the area and has launched a number of similar attacks near the capital in recent months.
The bombing came Iraqi military spokesman Yahya Rusoul announced the recapture of the town of Kubeisa from Daesh.
Earlier this month, a truck bomb exploded at a checkpoint in the city of Hilla, killing at least 47 people.
