Zinedine Zidane's agent says the France captain headbutted Marco Materazzi in Sunday's World Cup final because the Italian made a "very serious" comment.
Zidane appeared to react to something that was said and was dismissed for his violent charge into his opponent.
"He told me Materazzi said something very serious to him but he wouldn't tell me what," agent Alain Migliaccio told BBC Five Live Sport.
Sources in France say it is believed Materazzi insulted Zidane's family.
PARIS, July 10 (Reuters) - France captain Zinedine Zidane was apparently called a "dirty terrorist" by Marco Materazzi before he head-butted the Italy defender in Sunday's World Cup final, the anti-racism group SOS Racism said on Monday.
"According to several very well informed sources from the world of football, it would seem that the Italian player Marco Materazzi called Zinedine Zidane a 'dirty terrorist'," SOS Racism said in a statement.
Zidane, the son of Algerian immigrants, was shown a red card after the incident and Italy went on to win on penalties after the match was tied 1-1 following extra time.
The Paris-based group called for an inquiry and said world soccer's governing body FIFA had recently toughened sanctions against racism.
A lip-reader has reportedly revealed the words which provoked Zinedine Zidane's now infamous World Cup final headbutt.
Marianne Frere claims Italian defender Marco Materazzi insulted the French captain with a stream of racial and personal abuse.
She told The Sun that Zidane was called a "son of a terrorist whore" before he lashed out and was sent off.
Reports in France have suggested it was the reference to the Algerian-born star's mother which made him blow his top.
His mother Malika had been taken to hospital seriously ill only hours before Sunday's final.
Source: Reason for Zidane's headbutt
"I did not call him a terrorist. I am not a cultured person and I don't even know what an Islamist terrorist is."
Originally posted by xeroxed88
I think Italy would have still won if Zidane hadn't been sent off.
Zinedine Zidane will speak publicly for the first time after his controversial red card in the World Cup final, which France lost to Italy on penalties.
The 34-year-old will appear on French television at 1900 BST on Wednesday.
Fifa is to investigate Zidane's sending off for a headbutt on Marco Materazzi, which happened seconds after the Italian apparently insulted him.