BAMAKO (Reuters) - The death toll from an ambush on a Malian army convoy in the north of the country has risen to 33, the defence ministry said in a statement on Wednesday. Fourteen soldiers were also injured in the attack that took place Tuesday afternoon near the town of Tessit, in Mali’s northern Gao region. Islamist militants, many of whom have been linked to Al Qaeda and Islamic State, have stepped up attacks in Africa’s Sahel region in recent years, displacing thousands. Increased Islamist attacks, violence between rival ethnic groups and killings by security forces made last year Mali’s deadliest on record, data compiled by the Armed Conflict Location & Event Data Project (ACLED) showed.