Lionel Messi was unharmed after a youngster apparently threw a punch at him as he was leaving a restaurant in his home city of Rosario on Thursday.
The assailant was among a throng of people looking for autographs from the Barcelona star, a witness told Argentine TV. It was not clear if the punch landed, or what the intent was. Messi went on signing autographs.
"There was a crush of people waiting outside," Pablo Moyano, who was working in the restaurant, told Argentine TV. "There were kids, reporters, photographers waiting ... and one of the kids tried to punch him. I don't know if he pulled it off. He went running afterward."
Associated Press photographer Jose Granta also saw the incident and the youth racing off.
"Nothing serious happened," Granta said. "But the intent for some kind of aggression existed."
Other witnesses said the suspect was dressed in the uniform of a school a few streets away.
Messi tried to play down the incident on his Facebook page.
"To relax all those people that have asked us about the truth of the accident coming out of the restaurant, tell them I did not receive any blow from anyone. I'm perfectly OK," he wrote.
Messi arrived in Rosario, about 500 kilometers (300 miles) north of Buenos Aires, this week for a holiday before practice starts next week for the Copa America - the South American championship. The Copa America opens July 1 with Argentina facing Bolivia.