Protest organisers in Burundi urged African leaders meeting in Tanzania on Wednesday to demand that their president halt his bid for a third term, which has triggered the nation's worst crisis since an ethnically-fuelled civil war ended in 2005.
Protesters have taken to the streets for more than two weeks saying Pierre Nkurunziza's bid for another five years violates the constitution and the Arusha peace deal that ended the civil war. Both documents limit a president to two terms.
(READ MORE: Burundi opposition leader to run for presidency; protests pause)
More than 20 people have been killed since unrest erupted, according to an unofficial count by activists.
East African leaders and a top official from continental heavyweight South Africa met in Tanzania's commercial capital Dar es Salaam to discuss the crisis that has already spilled over into a region with a history of ethnic conflict.
More than 50,000 people have fled to neighbouring states. The U.N. refugee agency UNHCR said the crisis was heading towards a "worst case scenario" that could see 300,000 people fleeing, some to other parts of Burundi and others abroad.
That would mean displacing about 3 percent of the 10 million-strong population in one of Africa's most crowded nations.
"We expect the east African heads of state to tell President Nkurunziza that the constitution of Burundi and the Arusha peace agreement do not allow him to run for a third term," Pacifique Nininahazwe, a civil society activist and protest leader, told Reuters.
Nkurunziza, 51, who once led a rebel group from the majority Hutu population against the minority Tutsi-led army in the war, has pointed to a constitutional court ruling that said his first term did not count as he was chosen by lawmakers, not voted in.
Protesters say the court was manipulated and Britain and other donors have questioned the court's neutrality.
His bid and the mounting violence have drawn increasingly strong rebukes from Western nations and African colleagues. The United States, a major donor to the national army, said police must stop using "violent force" against protesters.
European states, big supporters of the budget, have withheld some aid, part of it related to a parliamentary vote scheduled for May 26 a presidential poll on June 26.
Police have regularly fired tear gas, water cannon and, say protesters, live rounds at demonstrators, who have hurled stones and barricaded streets in the capital. The police deny shooting.
Wednesday's summit host, Tanzanian President Jakaya Kikwete, whose country played a key role in ending Burundi's conflict, has criticised the third-term bid. In March he said that violating the constitution and Arusha deal risked violence.
(READ MORE: Burundi protests continue against Nkurunziza)
South African Deputy President Cyril Ramaphosa lends extra weight, as his nation was another vital player in the Arusha accords. While in office, Ramaphosa has helped defuse tensions in Lesotho and sought to broker peace in South Sudan.
Also among those attending will be President Paul Kagame of Rwanda, a nation with the same ethnic mix as Burundi that suffered a 1994 genocide in which 800,000 mostly Tutsis and moderate Hutus were slaughtered.
Kagame has often said he would not allow another genocide in the region. Analysts say his nation could be pulled into any new conflict where Tutsis are targetted.
About half the refugees have fled to Rwanda, many of them Tutsis who say they feel threatened by Imbonerakure, the youth wing of Nkurunziza's ruling party. The party denies any threats.