The new figure would make the assault, in which civilians were shot dead as they dug trenches to defend the remote town of Barsalogho, one of the deadliest single attacks in Africa in recent decades.

Up to 600 people were shot dead in a matter of hours by al Qaeda-linked militants in an August attack on a town in Burkina Faso, according to a French government security assessment that nearly doubles the death toll cited in earlier reports. The new figure would make the assault, in which civilians were shot dead as they dug trenches to defend the remote town of Barsalogho, one of the deadliest single attacks in Africa in recent decades.