Following a spate of mortar rounds fired at the Aguelhok camp, two military vehicles were dispatched and hit an explosive device "that led to the death of a blue helmet," the UN mission in Mali, MINUSMA, said.
MINUSMA said a number of other soldiers were wounded in the blast, including five who were seriously hurt.
Northern Mali fell into the hands of jihadists linked to Al-Qaeda in early 2012.
Analysts say tribal rivalries have led to a deterioration of the security situation in the north.
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A UN soldier was killed and four others were injured on August 7 when their vehicle struck an explosive device in Mali's northeastern Kidal region. The dead soldier and the injured were from Chad.
The UN deployed peacekeepers in July 2013, but the mission has been a relentless target for attacks.