Burundi's opposition said it is quitting U.N.-sponsored peace talks with the government after one of its leaders was gunned down in a drive-by shooting.
Zedi Feruzi of the Union for Peace and Development party was buried Sunday, a day after he and a bodyguard were shot to death in the capital, Bujumbura.
Thousands of opposition members accompanied his coffin thorough the downtown streets to a Muslim cemetery.
Another opposition leader, Frederick Bamvuginyumvira, bitterly said that his party can no longer hold talks with the government.
"It is impossible. We have decided to leave the negotiations because they are of no use...the most urgent thing is to cease the killings we are seeing and the organized assassination of opposition leaders."
The spokesman of another opposition party said he cannot guarantee that anti-government protesters will stay peaceful.
United Nations Secretary General Ban Ki-moon has condemned Feruzi's murder and is urging all parties to shun violence and work to resolve the country's political crisis.
Burundi authorities have violently cracked-down on anti-government protesters, who are angered by President Pierre Nkurunziza's announcement that he will seek a third term in next month's election.
Critics say a third term would be unconstitutional and violate the two-term limit.
Nkurunziza insists he is eligible to run again because parliament, not voters, elected him to his first term in 2005.
His plans for another five-year term has plunged Burundi into its worst crisis since a 2006 peace deal ended more than a decade of civil war.
The government's violent reaction to the protests has killed more than 20 people, brought on a failed coup, and sent more than 100,000 Burundians fleeing to safety in neighboring countries.
On top of the violence, the U.N. refugee agency says an outbreak of cholera has killed 31 Burundian refugees near Lake Tanganyika in Tanzania. Three-thousand other people have been sickened. Officials have brought in clean water and medicine.