Burundian opposition leader Agathon Rwasa filed on Thursday a case at the constitutional court challenging the May 20 presidential election outcome, saying he had evidence of fraud.

Burundi’s election commission said on Monday the ruling party candidate, retired General Evariste Ndayishimiye, had won the presidential election with 69% of votes cast.

We have provided evidence that there has been a massive fraud,” Rwasa told reporters after filing his complaint.

Hundreds of Burundians were killed and hundreds of thousands exiled after unrest surrounding the last election in 2015, when the opposition accused Nkurunziza of violating a peace deal by running for a third term.

Rwasa said the evidence in his filing showed that people had voted using dead voters’ identities and use of an electoral register which has never been published by the electoral body and ballot box stuffing.