Burundi's top court has made a ruling aimed at ending the power vacuum created by the sudden death of President Pierre Nkurunziza on Monday.
The Constitutional Court said has that President-elect Evariste Ndayishimiye should be sworn in as soon as possible.
Legally, the speaker of parliament, Pascal Nyabenda, should have become the interim leader.
But the cabinet decided to refer to the court and now Mr Ndayishimiye is due to become president two months early.
He was elected in May to replace President Nkurunziza, who had been in power for 15 years.
Burundi's top judges said that in the constitution the interim period under the speaker of parliament was designed as a time to hold fresh elections, but the president-elect's recent victory made this unnecessary.
The ruling ends days of uncertainty about the succession in the small East African country, reports the BBC's senior Africa correspondent Anne Soy.