Three demonstrators were killed in northern Mali on Tuesday, a medical source said, in a protest centered on a contentious peace accord that Mali has been struggling to enact.

Three demonstrators were killed in northern Mali on Tuesday, a medical source said, in a protest centered on a contentious peace accord that Mali has been struggling to enact.

Demonstrators said security forces opened fire when hundreds of young people set off on a banned march in the city of Gao.

A hospital source told AFP by phone that "the latest toll is three dead", with 31 injured.

The protest was linked to the implementation of a year-old peace deal signed by the government, loyalist militias and the Coordination of Azawad Movements (CMA), a coalition of rebel groups.

It was aimed at ending unrest in the country's vast desert north, which in 2012 fell under the control of three radical extremist groups, subsequently plunging the entire country into chaos.