“People should not see this as allowing the president to have some particular power, but to give the president power to be a full president,” said Jean Claude Karerwa, Mr. Nkurunziza’s spokesman.
Preliminary figures indicate that more than 80 percent of voters approved the change, after a campaign that critics said was undertaken in a climate of intimidation and abuse.
“There’s a risk in voting no,” said Evariste Ngayimpenda, who leads an opposition faction of the Uprona political party. “But there is a bigger risk in not voting at all.”
Opposition leaders said votes from the referendum on Thursday had been counted in many parts of the country without their observers present. The national election commission has not released official figures and has not said when it will do so. The figures released so far were compiled by journalists and civil society observers who had fanned out at polling stations across the country.
In addition to extending the presidential term, Burundi’s new Constitution will outlaw extradition, an article widely seen as taking aim at the International Criminal Court in The Hague. Burundi became the first country to withdraw from the court, in October, shortly after a United Nations report found evidence of extrajudicial killings, disappearances, arbitrary arrests and detentions, torture and sexual violence in the years since Mr. Nkurunziza took a third term in office.