Iraq said on Monday it has detained a top leader of the Islamic State group and a longtime al-Qaida operative in a cross-border operation.

Iraqi Prime Minister Mustafa al-Kadhimi tweeted the news, identifying the man as Sami Jasim, who oversees the Islamic State group’s financial operations and served as the deputy leader of IS under the late Abu Bakr al-Baghdadi.

Al-Kadhimi described it as “one of the most difficult” cross border intelligence operations ever conducted by Iraqi forces.

Jasim has a $5 million bounty on his head from the U.S. State Department’s Rewards for Justice program, which describes him as having been “instrumental in managing finances for IS terrorist operations.”

“While serving as IS deputy in southern Mosul in 2014, Jasim reportedly served as the equivalent of IS’s finance minister, supervising the group’s revenue-generating operations from illicit sales of oil, gas, antiquities, and minerals,” the website says.

Iraqi intelligence officials told The Associated Press that Jasim was detained in an identified foreign country and transported to Iraq few days ago. They spoke on condition of anonymity because they were not authorized to speak of the operation on the record.

Jassem worked with al-Qaida in Iraq leader Abu Musab al-Zarqawi, a Jordanian militant who was killed in a U.S. airstrike in Iraq in 2006. He assumed various security positions in Iraq, and moved to Syria in 2015, after the Islamic State group, an al-Qaida offshoot, declared its caliphate in 2014 and became the deputy of Abu Bakr al-Baghdadi, the extremist group’s leader.

Al-Baghdadi was killed in a U.S.-led raid in northwestern Syria in 2019, under former U.S. President Donald Trump.

Associated Press