Ahmad al-Faqi al-Mahdi, right, enters the International Criminal Court in The Hague, where he was sentenced to nine years in prison for the destruction of a UNESCO World Heritage Site in Timbuktu, Mali. (Pool photo by Bas Czerwinski via European Pressphoto Agency/Pool photo by Bas Czerwinski via European Pressphoto Agency)

An international court on Tuesday found an Islamist extremist guilty of committing a war crime for overseeing the destruction of historic mausoleums in the Malian desert city of Timbuktu and sentenced him to nine years in prison.

Ahmad al-Faqi al-Mahdi, a former teacher, had pleaded guilty and expressed remorse for his role in overseeing the destruction of nine mausoleums and a mosque door by rebels in June and July of 2012.

His trial, which began Aug. 22, was a landmark for the International Criminal Court, which has struggled to bring suspects to justice since its establishment in 2002. It was the tribunal’s first conviction for the destruction of religious buildings or historic monuments and the first guilty verdict delivered against an Islamist extremist.

Rebels affiliated with al-Qaeda occupied the fabled Saharan city of Timbuktu in 2012 and enforced a strict interpretation of Islamic law that included the destruction of the historic mud-brick tombs they considered idolatrous. Mahdi was a leader of one of the “morality brigades” set up by Timbuktu’s new rulers.

ICC prosecutors said he was a member of Ansar Dine, an extremist group with links to al-Qaeda that held power in northern Mali in 2012. The militants were driven out after nearly a year by French forces, which arrested Mahdi in 2014 in neighboring Niger.

The defendant said nothing after the verdict and sentencing. During the trial, he urged Muslims around the world not to commit acts similar to those he had admitted to.

“They are not going to lead to any good for humanity,” he said.

Mahdi had faced a maximum sentence of 30 years in prison for the destruction of the World Heritage sites. But presiding Judge Raul Pangalangan said numerous factors argued for a lesser prison term, including Mahdi’s initial reluctance to raze the historic shrines and what the judge called his apparently sincere admission of guilt.

The United Nations Educational, Scientific and Cultural Organization hailed the verdict as a crucial step toward ending impunity for the destruction of world cultural landmarks.

Soon after the destruction in 2012, UNESCO alerted the international community, including the ICC, “to ensure such crimes do not go unpunished,” UNESCO Director-General Irina Bokova said in a statement.

“In the context of repeated violence against people and their heritage, this sentence of the International Criminal Court is a key element in the broader response to violent extremism,” Bokova said.