Switzerland's attorney-general says banks have noted 53 possible money-laundering incidents in his investigation of the 2018 and 2022 World Cup bidding contests.

Michael Lauber says the "suspicious bank relations" were reported within the framework of anti-money laundering regulations.

He says he "does not exclude" interviewing FIFA President Sepp Blatter and secretary-general Jerome Valcke in the future.

Addressing the media for the first time since the Swiss investigation into FIFA was announced three weeks ago, Lauber says the case is "huge and complex."

Lauber declined to discuss a timetable for the case which targets "criminal mismanagement and money-laundering" in the bidding contests which sent the 2018 World Cup to Russia and the 2022 tournament to Qatar.

FIFA began the case by filing a criminal complaint against "persons unknown" last November.