"They were killed last night some 2 km (1.2 miles) from our regional headquarters in El Geneina. They came under fire from all sides," a spokesman for UNAMID said.
UNAMID, the world's largest peacekeeping mission, was deployed by the United Nations and the African Union in the arid western territory after fierce fighting in 2003 which forced hundreds of thousands of people to flee their homes.
A total of 42 peacekeepers have been killed since UNAMID was set up, according to the force.
Violence in Darfur, where mostly non-Arab rebels took up arms against the government in Khartoum, has ebbed from a 2003-04 peak but international efforts to broker peace have failed to end the conflict.