UPDATE: 11 a.m. EDT — Defense Secretary Ash Carter Friday confirmed that Haji Imam was killed in a recent U.S. raid in Syria. During a briefing, Carter highlighted recent successes against the Islamic State group, adding that a U.S.-led campaign has cut off revenue and the contingency of the so-called state.

"We are systematically eliminating ISIL’s Cabinet," Carter said, using an acronym for the extremist group.

Original story:

Haji Imam, a senior leader of the Islamic State group, has been killed by U.S. coalition forces, defense officials told NBC News on Friday. The leader’s death could mark a significant blow to the extremist group, also known as ISIS, as it continues to face military defeats in Iraq and Syria.

Imam, the nom de guerre for Abd ar-Rahman Mustafa al-Qaduli, was a deputy commander for the group and is believed to have served as second in command. Last year, Secretary of State John Kerry authorized a $7 million reward for information on his whereabouts.

The terrorist was reportedly killed during daylight hours in a U.S. special operations raid in Syria that was aimed at securing his arrest. Three others were reported dead. The news was first announced by the Daily Beast on Friday, which stated that Defense Secretary Ash Carter was expected to soon confirm the operation.

US: Abdul Rahman Mustafa al-Qaduli reported killed in Iraq with 3 others. pic.twitter.com/BTtAoylbXe — TAPSTRI MEDIA (@TAPSTRIMEDIA) March 25, 2016

Al-Qaduli was once a member of al Qaeda in Iraq, which later splintered into ISIS. Al-Qaduli previously served as the notorious al Qaeda leader Abu Musab al-Zarqawi’s right-hand man, according to Time. He allegedly acted as ISIS’ leader when Abu Bakr al-Baghdadi, the ISIS leader, was wounded. Many have speculated that he could have been next in line as the ISIS head. He was considered one of the group’s most experienced fighters and had considerable sway over day-to-day operations of the group, as al-Baghdadi has gone into hiding.

The news comes weeks after Tarkhan Batirashvili, better known as Abu Omar al-Shishani, was reported wounded in a U.S. airstrike. He is believed to have died shortly after. Batirashvili, an experienced Chechen fighter, is thought to have served as ISIS’ de-facto war commander.

The extremist group has faced setbacks on the battlefield in both Iraq and Syria in recent months. Militants have reportedly lost their hold on about a quarter of the territory they once held amid an intense U.S.-led airstrike campaign. At the same time, the extremists' influence internationally has expanded, particularly in Libya, and this week, supporters of the group carried out deadly attacks in Brussels, killing at least 31 people and wounding some 300.