At least 11 people were killed in clashes in west Ivory Coast including seven in an attack on a UN-protected displaced persons camp by angry youths, who torched the site despite the presence of the peacekeepers, sources said.
The United Nations condemned the attack, in which it said seven people were killed and 13 wounded, promising to boost its mission in the area. Earlier reports spoke of nine dead at the camp.
The UN secretary general's special representative in the country, Bert Koenders, deplored "this criminal act, a flagrant violation of international humanitarian rights".
However, he did not explain why the contingent of UN blue berets charged with protecting the camp had not been able to prevent the killings.
The deaths came after four people were killed in an attack late Thursday in the Kokoma district of Duekoue, inhabited mostly by ethnic Malinke.
Local sources said youths from Kokoma had later torched the displaced persons' camp at Niambly on the outskirts of town, populated mainly by Guere people, in an apparent revenge attack.
"They went to the camp, first of all destroyed the entrance, then burned down the camp," a security source said.
A staff member at the local hospital said "several dozen people" had arrived with knife wounds after the attack.
The 5,000 people who were in the camp had fled there during the post-election crisis sparked by ex-president Laurent Gbagbo's refusal to admit defeat to current leader Alassane Ouattara.
The Malinke are seen as Ouattara supporters, while the Guere are considered to be pro-Gbagbo.
Several sources said that the youths were accompanied by soldiers and traditional hunters who serve as auxiliaries to the army.
The UN mission in Ivory Coast was charged with guarding the Niambly camp but a staff member of the UNHCR refugee agency and a local journalist said the mission was overwhelmed by the crowd and "far too small".
"I cannot understand what happened for the UN not to be able to contain the crowd that was seeking revenge," said Cyprien Ahouret, a priest at Duekoue's Roman Catholic mission.
"When there is a crisis here, ethnic groups are taking advantage," he added.
Koenders called on national and local authorities to make greater efforts to ensure security in the region, adding that the UN mission would "immediately boost its presence on the ground".
A soldier said troops were looking for the "unidentified" people who had allegedly killed the four people in Duekoue. "We still haven't laid hands on them," he said.
Long prone to serious ethnic tensions based on land disputes, the west of Ivory Coast remains the most unstable part of the country more than a year after the end of the post-electoral crisis of December 2010 to April 2011, which claimed some 3,000 lives, including hundreds in the Duekoue region.
Several villages came under attack in early June south of Duekoue, close to the border with Liberia. More than 20 people were killed, including seven UN peacekeeping troops from Niger serving with the UN mission in Ivory Coast.