The UN peacekeeping mission in Mali (Minusma) has condemned the assassination of a rebel leader who was a signatory to a 2015 peace accord.
The mission said Sidi Brahim Ould Sidati "was an important player" in negotiations and implementation of the Algiers peace deal.
Ould Sidati was the head of Coordination of Azawad Movements (CMA) a mostly ethnic Tuareg alliance that rose against the government in 2012 seeking greater autonomy.
He was shot dead in the capital Bamako on Tuesday.
Correspondents say there are fears that his murder could undermine Mali's already shaky peace process.