One of the most troubling and mysterious episodes in recent French history - the brutal death of six French monks in Algeria in 1996 - is to be re-investigated with the co-operation of the French state.

Rumours have swirled for years around the kidnapping and decapitation of the Cistercian monks, which was blamed by authorities in Algiers and Paris on Islamist radical terrorists. New evidence presented to an investigating judge in France by a French general suggests...