Bujumbura - Burundi's president launched a campaign on Tuesday to support constitutional amendments that could extend his rule despite warnings by his opponents of more violence ahead.

President Pierre Nkurunziza told supporters in Gitega province to vote in favor of the changes in an upcoming national referendum. The proposed changes include extending a presidential term from five years to seven.

A date for the referendum has not been set but it is expected next year.

The opposition has warned that attempts to change the constitution could lead to more bloodshed in the East African country still reeling from deadly violence following Nkurunziza's contentious decision to seek a third term in 2015.

Hundreds of people have been killed, and the International Criminal Court has begun looking into alleged crimes.

The constitutional changes were proposed by a government-appointed commission and have been ratified by Nkurunziza's cabinet. Many Burundians believe that after the amendments become law Nkurunziza will attempt to serve two more terms totaling 14 years.

Burundi's most prominent opposition leader, Agathon Rwasa, told The Associated Press that "it's clear that Nkurunziza is aiming at remaining in office for life."

Nkurunziza "wants to tailor the constitution to his desire" to rule for several more years, said iBurundi, a group of online activists. "The regime is using this campaign to deflect the pressure following its refusal to engage in inclusive peace talks."

Nkurunziza rose to power in 2005 following the signing of the Arusha accords to end Burundi's 13-year civil war that killed about 300 000 people. He was re-elected unopposed in 2010 after the opposition boycotted the vote.

Nkurunziza said he was eligible for a third term in 2015 because lawmakers, not the people, had chosen him for his first term, but critics called the move unconstitutional. His current term expires in 2020.