Twenty five others were also injured in the attack.
The UN Multidimensional Integrated Stabilization Mission in Mali, also known as MINUSMA said the attack took place Aguelhok, Kidal region.
"The Secretary-General calls on the Malian authorities, as well as the signatory armed groups to the peace agreement, to spare no effort in identifying the perpetrators of this attack so that they can be brought to justice as swiftly as possible," according to a UN statement.
Al-Qaeda in the Islamic Maghreb (AQIM) claimed responsibility for Sunday's attack.
Mali, one of the poorest countries in the world, suffers from the presence of several terror groups, where French, Malian and UN peacekeepers are conducting counterterrorism operations.
Tensions erupted in Mali in 2012 following a failed coup and a Touareg rebellion that ultimately allowed al-Qaeda-linked militant groups to take over the northern half of the country. In 2015, a peace deal was signed between the government and some insurgent groups.
Political and community disputes continue to fuel tensions in northern Mali, thus undermining the implementation of the peace agreement.