Zinedine Zidane, the French soccer player who stunned the world when he head-butted an Italian player in Sunday's World Cup final, says his victim insulted his mother and sister.

During an appearance on French television, Zidane apologized and touched on the reason for his attack on his Italian opponent Marco Materazzi. However, Zidane did not go into detail about exactly what words were exchanged.

He said it was "very personal and concerned his mother and his sister."

However, the French soccer legend acknowledged his behaviour was inexcusable.

"I want to ask for forgiveness from all the children who watched that," he said. 

"There was no excuse for it. I want to be open and honest about it."

Materazzi is at odds with Zidane on the nature of what was said. He has been up front about the fact he insulted him, but has rejected suggestions he called him a terrorist or made reference to his mother.

The head-butt caused soccer fans around the world to wince in pain and scratch their heads in bewilderment.

In the days following, soccer analysts, journalists and fans have speculated about what Materazzi may have said to Zidane in the seconds before he was knocked to the ground. Some have suggested Materazzi made racist remarks in reference to Zidane's Algerian heritage, or insulted his mother.

The incident came during extra time as the two teams grappled to end a hard-fought 1-1 tie.

Zidane and Materazzi traded words after Italy intercepted a French scoring attempt. Zidane then trotted casually ahead of the Italian, turned around to face him, lowered his head and rammed him squarely in the chest, catching Materazzi off-guard and instantly knocking him to the ground.

Zidane received a red card and was ejected from the game.

It was a stunning way for Zidane -- who had intended for the World Cup to be his final professional match -- to end his legendary career.

The Italians went on to win the match 5-3 on penalties.

Zidane received the World Cup best player award, but there are suggestions he may be stripped of the honour pending a Fifa investigation.

The president of the organization, Sepp Blatter, has ordered an investigation into the circumstances of the conflict.

Blatter told La Repubblica newspaper that the recipient is chosen by an international panel of journalists, but Fifa has a responsibility to intervene if the decision could hurt the sport.

"That is why I gave the orders to our disciplinary commission to investigate what happened," Sepp told the newspaper.

"To see him acting like that leaves me vexed, both for himself and for all sense of fair play."