Burundi civil society groups called Friday for voters to boycott "sham elections", after opposition parties said they would not take part because fair polls were impossible after weeks of violence.

Civil society leaders issued a joint statement calling on the international community "not to recognise the validity" of the polls.

Parliamentary elections are due to be held on Monday and a presidential vote on July 15, when President Pierre Nkurunziza will bid to serve a third consecutive five-year term.