President Pierre Nkurunziza of Burundi, aged 55, has died of a heart attack, the government official says.
A government statement says that he was admitted to hospital on Saturday after feeling unwell.
His condition then improved but on Monday he had a cardiac arrest and efforts to revive him were unsuccessful.
He has been in power in Burundi since 2005.
Nkurunziza was the Chairman of the National Council for the Defense of Democracy-Forces for the Defense of Democracy, the ruling party, until he was elected as President of Burundi.
Nkurunziza was due to step down from the presidency in August after 15 years in power.
Details later…