Burundi's electoral commission says a majority of voters agreed to amend the constitution in changes that could prolong the rule of President Pierre Nkurunziza until 2034.

The electoral commission announced Monday that more than 73 percent of voters in the May 17 referendum supported the constitutional amendments.

Nkurunziza had campaigned forcefully for the constitutional changes that include extending the president's term from five years to seven, making him the latest African leader to prolong his stay in office. He can now run for two more terms when his current tenure expires in 2020.

On Saturday the leader of a Burundian opposition coalition said he would reject the outcome, calling the vote undemocratic.

Burundi has seen deadly political violence since 2015 when Nkurunziza announced he would seek a third term.