1016 Ismaili massacre in Ifriqiya
The 1016 Ismaili massacre in Ifriqiya was a massacre of the Isma'ili Shia Muslim inhabitants of Ifriqiya (modern-day Tunisia, eastern Algeria and western Libya) by Sunni Muslims under the leadership of Maliki jurists and scholars. Sunni riots started in October 1016 in Qayrawan and later spread to other towns, killing about 20,000 Shi'ites.
Source: Wikipedia — 1016 Ismaili massacre in Ifriqiya (CC BY-SA 4.0)