The United Nations refugee chief said Wednesday he was "extremely worried" at the political crisis in Burundi, where at least 30,000 refugees have fled ahead of elections.

"We thought Burundian refugees were something we would never have to discuss again, unfortunately we are back to having a significant outflow of Burundians," UN Refugee Agency (UNHCR) chief Antonio Guterres told reporters. "It must stop - we have enough crises in the world."