<p>Twenty-five years after 9/11, figures compiled by conflict monitor underline how Sahel region has become centre of Islamist terror</p><p>Islamist extremist violence in Africa’s Sahel region is set to reach historic highs after a series of sweeping offensives by groups linked to al-Qaida and Islamic State, according to new figures compiled by the conflict monitor <a href="https://acleddata.com/">Acled</a>.</p><p>As the US marks the 25th anniversary of the 9/11 attacks launched by al-Qaida agai