UN spokesperson Farhan Haq told reporters in New York the peacekeeper was killed in a battle with M23 rebels near the key eastern city of Goma.
The DR Congo army and UN troops launched an operation on Wednesday against the M23, who have been battling government forces around Goma since March last year.
The rebels have used positions on hills north of Goma to launch artillery attacks on the city.
UN troops, including from the landmark new offensive intervention brigade, fired mortars and used attack helicopters in the battle.
"The operation is ongoing and we have just heard that one UN peacekeeper has been killed and three others have been wounded," Haq said.
Pakistani troops part of the UN peacekeeping missions are also deployed in Congo.
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