The group was released in neighbouring Nigeria.

They include a Franco-Ivorian, a Senegalese, a Chadian and two of their Cameroonian security guards.

The charity group says they are now "safe and sound".

The aid workers were organising humanitarian aid activities in the northern town of Fotokol when armed men broke into their residence and abducted them in February.

MSF has not disclosed the circumstances of their release and it’s not yet clear who had abducted them.

But the militant group Boko Haram and its splinter faction known as Islamic State West Africa Province have been unleashing violence in the region.

The Islamist insurgency in Sahel region, which began in 2009, has killed hundreds of thousands and displaced millions of others in several countries.