The move means no one in the governing CNDD-FDD is allowed to disagree with his choices, secretary-general Evariste Ndayishimiye said.

"He is our leader. Therefore in our party... no one is comparable to him," Mr Ndayishimiye said.

"He is our parent, he is the one who advises us. That is why I ask all our members to respect that because a home without the man (its head) can be overlooked by anybody. For us, we have the best."

But critics say a cult of personality is developing around 54-year-old Mr Nkurunziza.

Jeremy Minani, the leader of the opposition Rally of Burundi Democrats (RDB), told Burundi Radio Publique Africaine: "President Pierre Nkurunziza's naming himself the leader of the ruling party, is part of his plan to reach his goal and to make it easy for him to eliminate every challenge without difficulty."

The new title has been bestowed just months ahead of a national referendum which could end with Mr Nkurunziza getting permission to rule until 2034. He is already serving a controversial third term in office.

His re-election led to violence in the streets in 2015, leaving more than 1,000 people dead and displacing hundreds of thousands.