A Kenyan observer with the United Nations peace mission in the Democratic Republic of Congo has been shot dead in the north-eastern region of Ituri.
President Kabila has said UN peacekeepers could leave this year
The UN said the attack took place on Thursday near the town of Bunia, when armed men opened fire on a UN convoy.
About 50,000 people have died in clashes between rival ethnic groups in the region in the last five years.
Some 10,000 UN troops are in DR Congo to monitor a peace deal which ended almost five years of war.
Relative peace has returned to most of the country, except mineral-rich Ituri.
Last week, UN troops were attacked there and more than 100 boat passengers were killed in January.
It is not clear who was responsible for the attack on the convoy but a UN spokesman said rival branches of the Union of Congolese Patriots (UPC) militia have been clashing in recent days.
The attackers were dispersed when a UN helicopter opened fire.
The UN Secretary General, Kofi Annan, said he was deeply saddened by the news of the peacekeeper's death.
On Monday, Congolese President Joseph Kabila said that security was improving so fast that United Nations troops could leave this year.
He told the BBC that the peacekeepers should instead start training DR Congo's army and police force.
An estimated three million people were killed in the war, which also drew in the armies of six neighbouring countries.
Former rebels have joined a power-sharing government, tasked with organising elections next year.