Burundi's President Pierre Nkurunziza, aged 55, has died after suffering a cardiac arrest, the government says.

A government statement says that he was admitted to the 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.

Mr. Nkurunziza was due to step down from the presidency in August after 15 years in power.