Burundi's newly elected president Evariste Ndayishimiye will be sworn in today (Thursday), following the sudden death of his predecessor Pierre Nkurunziza who left him an isolated nation in political and economic turmoil.

Ndayishimiye was elected in May, in a vote disputed by the opposition, and was meant to take office in August

But his inauguration was speeded up after his predecessor Nkurunziza's sudden death.

Nkurunziza, a devout evangelical who believed he was chosen by God to lead Burundi, leaves a "dark and sad legacy", Carina Tertsakian of the Burundi Human Rights Initiative told AFP.

He won the vote with 68.7 per cent and an opposition bid to have the results overturned due to alleged fraud was overturned just days before Nkurunziza's death.

After the news of Nkurunziza's death, Ndayishimiye vowed to "continue his high-quality work that he has done for our country".