A peacekeeper was shot dead Friday in an attack on an African Union-UN base in Sudan's Darfur, the mission said, two days after the government announced it regained control of the area from rebels.
"In the early morning hours of 19 April, one peacekeeper of the African Union-United Nations Mission in Darfur (UNAMID) was shot dead and two others injured in an attack by unidentified assailants on the mission's team site near Muhagiriya," mission spokeswoman Aicha Elbasri said in a statement.
UNAMID did not release the nationality of the victims but Muhagiriya falls under the jurisdiction of Nigerian peacekeepers.
"UNAMID is investigating the events surrounding the incident and working in coordination with (the) government of Sudan to ensure that the perpetrators are brought to justice, as any attack on international peacekeepers is a crime under international law," Elbasri said.
More than 40 peacekeepers have been killed in hostile action during UNAMID's five-year history and the UN has repeatedly called for the perpetrators to be brought to justice
However, UN sources have said they were unaware of anybody previously being held accountable in Sudan for killing a peacekeeper.
In February a UN panel of experts reported that former members of government militias "have forcibly expressed their discontent with the current government," including through occasional cases of "direct attacks on UNAMID staff and premises".
Ethnic rebels in Sudan's far-western Darfur region rose up against the Arab-dominated Khartoum government in 2003.
In response, the government-backed Janjaweed militia shocked the world with atrocities against ethnic Africans.
While the worst of the violence has long passed, instability has been complicated by inter-Arab fighting, kidnappings, carjackings and other crimes, many suspected to be the work of government-linked militia and paramilitary groups.
A rare 10-day rebel occupation of Muhagiriya and Labado in southern Darfur ended on Wednesday when the Sudanese army announced it "liberated" the area but the insurgents said they withdrew in the face of massive force.
The Sudan Liberation Army's Minni Minnawi faction on April 6 took control of the two communities strategically located about 100 kilometres (60 miles) east of the South Darfur state capital Nyala, one of Sudan's largest cities.
Darfur's insurgents normally stage hit-and-run attacks.
"Yes, we withdrew from Muhagiriya and Labado," said rebel spokesman Abdullah Moursal.
He said the government sent two "huge" convoys of troops, one from the west and one from the east, and these were backed by air strikes.
The government had already regained control of Labado on Tuesday after fierce fighting which resulted in the deaths of four civilians and the wounding of six others, UNAMID said.
Thousands of civilians had sought shelter around UNAMID bases in the district since the initial fighting, and the UN had been calling for access to assist them.
Rebel splinter factions signed a 2011 peace deal with the government but Minnawi and other major insurgent groups rejected the agreement.
Sudanese Interior Minister Ibrahim Mahmoud Hamed said in statements published Thursday that Darfur is largely calm "except some looting operations carried out by the rebel movements" and attacks on commercial convoys.
But Vice President Ali Osman Taha last Sunday warned over insecurity in South Darfur.
Security in Darfur has "worsened", Canada said at a conference last week in Qatar.
Although violence continues, UN officials say parts of Darfur are "relatively stable" and offer good opportunities for rebuilding after a decade of war.