THE HAGUE, Netherlands -- An international court on Tuesday found a Muslim radical guilty of committing a war crime by 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 pickax-wielding rebels in June and July of 2012.

His trial, which opened 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 destruction of religious buildings or historic monuments, and the first guilty verdict delivered against a Muslim extremist.

UN Secretary-General Ban Ki-moon welcomed the court's ruling as "an important step forward in the fight against impunity in Mali," according to a statement released by Ban's spokesman.

Al Qaeda-linked rebels occupied the fabled Saharan city of Timbuktu in 2012 and enforced a strict interpretation of Islamic law that included destruction of the historic mud-brick tombs they considered idolatrous. Al Mahdi was leader of one of the "morality brigades" set up by Timbuktu's new rulers.

ICC prosecutors said Al Mahdi was a member of Ansar Eddine, an Islamic 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 Al Mahdi in 2014 in neighboring Niger.

Clad in a gray suit and striped purple tie, the defendant said nothing after the verdict and sentencing. Earlier in the trial, Al Mahdi 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.

Al Mahdi had faced a maximum sentence of 30 years in prison for destruction of the World Heritage-listed sites. But presiding judge Raul Pangalangan said numerous factors argued for a lesser prison term, including Al 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 International Criminal Court "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.

Al Mahdi's conviction "is a first important step toward the fight against impunity in Mali," said Drissa Traore, vice president of the International Federation for Human Rights.

"But this victory has an almost unfinished look ... We hope ICC will continue to investigate and prosecute those responsible for the most serious crimes committed in Mali, especially crimes of sexual violence."