The Swiss attorney general said on Wednesday his office has seized around nine terabytes of data as part of an major investigation into suspected irregularities in the allocation of the FIFA World Cups of 2018 and 2022.

"Our investigation is of great complexity and quite substantial. To give you an example, the OAG (Office of the Attorney General) has seized around nine terabytes of data," Swiss Attorney General Michael Lauber said at a news conference in Berne.

"So far our investigative team obtained evidence concerning 104 banking relations. And be aware that every banking relation represents several bank accounts."

Lauber spoke publicly for the first time since the OAG seized data and documents stored in computer systems at FIFA last month as part of criminal proceedings related to the allocation of the 2018 and 2022 FIFA soccer World Cups, which were awarded to Russia and Qatar respectively.