Mali's president Ibrahim Boubacar Keita on Monday declared three days of mourning after a militant attack on an army base killed more than 40 soldiers last week in one of the deadliest strikes on the country's military. Islamic State-allied militants claimed Friday's attack on Indelimane base in the northeast of the country near the border with Niger, which authorities say killed at 49 soldiers.It was the latest assault on target Mali's military which is struggling to contain an Islamist insurgency that began in the north and spread to the centre of the country. At least 40 troops were killed a month ago in a double attack near the Burkina Faso border. A presidential communique read on national radio said Boubacar had declared three days of mourning, though the Malian leader has still has not spoken publicly about the Indelimane attack.Islamic State-allied militants claimed responsibility for the Indelimane strike during which gunmen on motorbikes attacked the base in three different groups, according to Malian army sources and a UN document seen by AFP.Over the weekend two more Malian soldiers were also killed by a roadside bomb and a French soldier was also killed when his vehicle hit an improvised explosive device.Northern Mali fell into the hands of jihadists in 2012 before the militants were forced out by a French-led military intervention. But the jihadists have regrouped to carry out hit-and-run strikes in violence that has spread to central Mali. France still has around 4 500 troops in the country as part of its Barkhane operation and is looking to hand more responsibility to local forces.French Armed Forces Minister, Florence Parly, on an official visit to the Sahel called for "patience" in the battle against the militants."This is a fight where we have to have patience," she said on a visit to Barkhane operations in the Chad capital N'Djamena. "We still need time for the local forces to build up their resilience."Neighbouring Burkina Faso and Niger have also been infiltrated by insurgents, at the cost of hundreds of lives.The G5 Sahel, a five-nation joint taskforce set up in 2014 to tackle the jihadist threat, is also active in the region. It comprises troops from Burkina Faso, Mali, Mauritania, Niger and Chad.