Four United Nations peacekeepers from Chad were killed on Tuesday when their truck was blown up in Mali, casting a shadow over the restart of peace talks between the west African state and rebel militias.
The incident comes a day after negotiations began between the government and six armed rebel groups in the Algerian capital aimed at clinching a lasting peace agreement in the restive, deeply-divided nation.
"Four peacekeepers from Chad are reported to have been killed. Fifteen others have been wounded, including six who are reported to be seriously injured," UN spokesperson Stephane Dujarric said.
Their vehicle "hit an explosive device" in the northeastern desert region of Kidal, he added.
Riven by ethnic rivalries, a Tuareg rebellion and an Islamist insurgency in its vast desert north, Mali has struggled for stability and peace since a military coup in 2012.
The Bamako government and various rebel groups, mostly Tuareg but also including Arab organisations, are seeking to resolve a decades-old conflict that created a power vacuum in the desert north that was exploited by Al-Qaeda.
Armed groups in desert
The National Movement for the Liberation of Azawad (MNLA) and the High Council for the Unity of Azawad (HCUA) have launched four uprisings since 1962 to fight Mali's army over the territory they claim as their Tuareg homeland and call Azawad.
A ceasefire had been in force since May, when the rebels seized a large swathe of northern Mali in a major offensive.
Since President Ibrahim Boubacar Keita came to power last year negotiations have stalled and northern Mali has seen a spike in violence by Islamist and separatist militants.
Skirmishes in May between the Malian army and a coalition of rebels from the MNLA and HCUA saw at least 50 soldiers killed in Kidal, a stronghold of the Tuareg people.
A ceasefire secured by Mauritanian leader and African Union chief Mohamed Ould Abdel Aziz has been in place since, but the Malian government has expressed alarm at the "concentrations of armed groups" in the desert.
The talks are being held with a new defence agreement in place between Mali and its former colonial power France.
Paris recently wound up Operation Serval, its military offensive launched in January 2013 to oust Al-Qaeda-linked Islamists who had occupied northern Mali.
Serval has been replaced by a wider counter terrorism operation, codenamed Barkhane, to be implemented in partnership with Mauritania, Mali, Burkina Faso, Niger and Chad.
French defence minister Jean-Yves Le Drian has said around 3,000 French soldiers will be part of the operation, 1,000 of whom will stay in northern Mali.
Drones, helicopters, fighter jets, armoured vehicles and transport planes will also take part in Operation Barkhane -- the name of a crescent-shaped sand dune in the desert -- which will have its headquarters in the Chadian capital N'Djamena.