Burundians began voting for or against the amendment of the country’s constitution on Thursday morning.
They will be ticking in a YES box to amend or NO box not to amend the 2005 constitution.
On the eve of the polls, security was beefed up with police and soldiers seen patrolling the streets in the capital Bujumbura.
At Kamenge in Bujumbura, a stronghold of the ruling CNDD-FDD party, voters began queuing before polling stations opened.
“We are here to exercise our rights and the new constitution will be able to bring unity and stability in the country,” said Kitegesi Janvier, a Kamenge resident who was among the first to cast his vote.
The country had last amended the constitution in 2005 when President Pierre Nkurunziza took the office.
The current law has been at the centrestage of the political crisis that erupted in 2015 after President Nkurunziza vied for another term which opponents said violated the constitution and the Arusha Accord.
Burundi signed a peace agreement in Arusha in 2000 that ended a civil war in which about 300,000 people were killed.
Opposition and rights group say the campaign season had been marked by repression of those against amending the supreme law.
“Despite all the intimidation and threats, people will decide their own destiny. This is not the first time there is a big challenge; in 1961, 1993, 2005 and even today,” Agathon Rwasa, the opposition leader, told The EastAfrican before leaving for Ngozi in northern Burundi, his home town to cast his vote.
Mr Rwasa, who is the deputy speaker of the parliament, is among the opposition leaders campaigning against the constitution amendment.
He has, however, criticised opposition members outside the country who were calling on Burundians to boycott the referendum.
“You cannot be called a true opposition when you are outside the country. For us here we really understand the real issues and challenges Burundians are facing so boycott is not a right thing,” he said.
If Burundians vote to amend the constitution, presidential terms will be lengthened to seven years from five and would also allow President Nkurunziza to extend his rule to 2034.
Another law to be amended will be one that will prohibit extradition of citizens for prosecution in foreign courts such as the International Criminal Court.
Some 4.8 million people have signed up to vote, according to the Independent National Electoral Commission (CENI).