UN agencies have launched an appeal for more than $200 million US to help people fleeing conflict in Burundi, saying since April alone almost 100,000 people have been affected.

Willy Lowry travelled to Kigoma, Tanzania, to speak with some of the people who fled the country and are now struggling with limited shelter, food and clean water.

In another development, the leader of a Burundi opposition party was killed Saturday by unknown assailants in the nation's capital, Bujumbura, local media reported.

Iwacu, a prominent news organization in Burundi, reported on its website that Zedi Feruzi of the UPD-Zigamibanga party was slain late Saturday in a drive-by shooting in which at least one of his bodyguards was also killed.

Feruzi's killing, which took place in Bujumbura's Ngangara district, is likely to raise tensions in this Central African country that has been hit by political unrest since the announcement late last month that President Pierre Nkurunziza would seek a third term in office.

At least 20 people have died and 431 people have been wounded in street protests against the president's decision to run in the elections scheduled for June 26.