The identity of Friday's attackers, who wore no uniforms, was not known. Suspicion fell on Lendu militia belonging to the group Patriotic Force of Resistance in Ituri, responsible for several massacres in the region.
The group's former commander, Germain Katanga, was recently made a general in the Congolese army through a 2003 power-sharing agreement that ended the civil war.
The Ituri conflict came amid Congo's larger war and the transitional government has struggled to extend its authority to the long-ungoverned east.
Prior to Friday's killings, 45 UN peacekeeping personnel had been killed in the Congo mission since 1999, according to the UN.
UN peacekeepers frequently have been targeted on missions around the world. Among the deadliest attacks came in Somalia, on June 5, 1993, when 24 Pakistani soldiers were killed in an ambush as they checked a weapons storage site.
Ten Belgian peacekeepers were slain at the start of the Rwanda genocide on April 7, 1994.
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