The attack took place yesterday at North Kivu province's Beni town - some 600 metres south from battalion headquarters, it said.
The personnel were "injured in the grenade attack by unknown assailants on a motorcycle in a remote region of the war-torn African nation", Nepali Army said in a statement.
The condition of two personnel was critical, said army spokesperson Brig Gen Jagadish Chandra Pokharel.
Nepali peacekeepers have been deployed in Congo since 1999, under the UN peace keeping mission.