The inscription of voters for a constitutional referendum that could allow Burundi's president to prolong his rule began Thursday in Burundi, the independent national electoral commission (CENI) announced.
If accepted by the electorate, the constitutional change passed by the government last October would enable President Pierre Nkurunziza, in power since 2005, to stand for two further terms of office from 2020.
All opposition parties are opposed to a referendum in May on changes that they say might be a death warrant for the Arusha peace accord of 2000, which opened the way to an end to prolonged civil war (1993-2006) at the cost of more than 300,000 lives.
The new electoral register also concerns youths who will come of age by 2020, so they can vote in general elections due that year, the CENI said.
"Census agents will be in registration centres every day from 7.30 until 17.30, even on Saturday and Sunday," until February 17, CENI president Pierre-Claver Ndayicariye said Thursday on national radio.
The commission has deployed 11,583 agents to register an anticipated 4.5 million voters, compared with 3.5 million for elections in 2015.
UN Secretary-General Antonio Guterres has criticised the determination of Burundi's current rulers to reform the Constitution without taking account of the views of the opposition in the small, densely populated central African nation.
When Nkurunziza said he planned to run again for office in April 2015, the opposition challenged the move as unconstitutional since he was not allowed a third term.
His supporters countered that his first term was a parliamentary appointment, not an election result.
Protests and a foiled coup bid turned violent as Nkurunziza's third term caused a political crisis that has since claimed at least 1,200 lives and displaced more than 400,000 people.