FIFA said that it rejected about 50 fake tickets for the opening World Cup match in Sao Paulo between host Brazil and Croatia.

FIFA marketing director Thierry Weil said the tickets for yesterday's game were "an example of real professional fakes, not the poor imitations made in a copying machine." And he's guessing there are more.

"Even for us, it's extremely complicated to see if it's a fake ticket or a real ticket," Weil said. "We need to communicate to the fans that there are tickets going around that are fake tickets that are extremely difficult if not impossible to recognise."

Weil held up a ticket that looked identical to an authentic ticket. He said it might even include the electronic chip, although a chip that would not work and would be detected when it was scanned entering the stadium.

He said some matches might be targeted more than others by counterfeiters, but did not say which matches they might be.

"You have no pleasant time when you have a family, father, mother and three kids coming, and you have to reject them. But we have to because they are fakes."

He said those detected on yesteday must be the tip of the iceberg.

"Based on the quality of how they are done, there must be far more tickets in circulation than only those 50."