Ms Rwigara, who was arrested on Friday, has been under investigation over alleged forgery.

Authorities have also investigated her family over alleged tax evasion. Police spokesperson Theo Badege said in a statement on Sunday that Ms Rwigara had been arrested for failing to co-operate with the police:

The decision to arrest was in addition to the behaviour of the suspects during preliminary investigations, particularly their consistent refusal to co-operate with the police and publicly revealing information that is, by law, supposed to be confidential.”

He added that she could be held for five days:

"The criminal procedure law gives investigators powers to detain a suspect for a maximum of five days in order to conclude investigations and decide, based on the evidence, whether or not to forward the case to prosecution.”

On Monday morning, a local website alleged that members of the Rwigara family were involved in a plot to overthrow the government, working with exiled groups including the Rwanda National Congress (RNC), the East African reports."

Ms Rwigara has previously denied working with exiled opposition groups, it adds.

Ms Rwigara was disqualified as a candidate in last month's presidential race which was won by incumbent President Paul Kagame. Investigators allege that Ms Rwigara committed an electoral offence by collecting forged signatures to endorse her candidacy.

She has denied the accusation.