GENEVA (AFP) - Swiss police on Wednesday raided the headquarters of Fifa, seizing documents in a probe linked to fraud in the awarding of the 2018 and 2020 World Cups, the Swiss attorney-general's office said.

The raids follow the shock dawn arrest of six top football officials in Zurich, where Fifa is headquartered, only two days before its president Sepp Blatter seeks re-election as head of football's world governing body.

Documents and electronic data were seized as part of an investigation already underway into money laundering and fraud involving Fifa's awarding of the 2018 and 2022 World Cups to Russia and Qatar respectively, a statement said.

It said 10 people would be questioned "who took part in the voting on the allocation of the 2018 and 2022 World Cups as members of the Executive Committee."

The probe, which was launched on March 10 this year, was not made public until now.