Geoffrey Dieudonne, an official with the parliament of Belgium's French-speaking community, had been in Mali for a convention, the parliament said in a statement.
"Mr Dieudonne, with other foreign colleagues, was in Mali to give a seminar for Malian parliamentarians," the Brussels-based parliament said.
"At this stage the exact circumstances of his tragic death are not yet known."
18 bodies have been recovered so far from the siege, a foreign security source told AFP. The gunmen are holding no more hostages, Mali's security minister said.