ISIS' finance minister was killed during an operation this month, defense officials announced Friday, a major score for the U.S.-led coalition as it tries to erode the terror group's grip on the region. In addition to the death of Haji Imam this month, the Pentagon confirmed the killing of another top leader — Omar al-Shishani — in an earlier raid.

This image made from undated video posted during the weekend of June 28, 2014 on a social media account frequently used for communications by the Islamic State of Iraq and the Levant (ISIL), which has been verified and is consistent with other AP reporting, shows Omar al-Shishani standing next to the group's spokesman among a group of fighters as they declare the elimination of the border between Iraq and Syria. AP

"Striking leadership is necessary, but it's far from efficient," Defense Secretary Ash Carter said at a news conference, adding that the U.S. is "systematically eliminating" ISIS' cabinet. "Leaders can be replaced, however, these leaders have been around for a long time," Carter said. "They are senior. They're experienced. So eliminating them is an important objective and achieves an important result." Haji Imam — whose real name is Abd al-Rahman Muhammad Mustafa al-Qaduli — was widely reported as a senior leader and second in command in the organization.

Carter, however, declined to provide further details about the operations, and didn't immediately confirm where and when exactly the efforts to kill Haji Imam took place. Haji Imam oversaw and steered ISIS' funding through its networks, Carter said. He also reportedly managed the day to day operations for ISIS and its affiliates in Syria, Iraq and Libya, and was also the main link to shadowy ISIS leader Abu Bakr al-Baghdadi, who currently has minimal communication with the organization.

The confirmed deaths of Imam and al-Shishani present a key gain in ticking off some of the biggest names on the U.S.'s terror hit list and comes on the heels of terror attacks in Brussels that claimed at least 31 lives and wounded over 270 others. Carter said he could not confirm whether Haji Imam was directly involved with Brussels or the siege last November in Paris, which intelligence officials say were done by the same ISIS-linked terror cell. Either way, he said, those involved are examples of ISIS recruits from outside Syria and Iraq who serve as foreign fighters and then return to their homelands to unleash terror. In other cases, homegrown terrorists are simply inspired to do ISIS' bidding, Carter added. "Even if it's just inspiration, it still takes you back to Iraq and Syria and the need to eliminate the sources for that inspiration," the defense secretary said.