US Secretary of Defense Ash Carter (L), together with Chairman of the Joint Chiefs of Staff Gen. Joseph Dunford, speaks to press during a briefing at the Pentagon in Washington D.C., the United States, on March 25, 2016.[Photo/Xinhua]

WASHINGTON -- The Pentagon announced on Friday a senior Islamic State (IS) commander in Syria believed to be in line to lead the extremist group had been killed by the United States.

Abd al-Rahman Mustafa al-Qaduli, also known as Haji Imam or al-Afri, served as IS's finance minister, and was killed this week by US military, US defense chief Ash Carter said here at a Pentagon briefing.

"We've taken out the leader who oversees the funding for ISIL's operations, hurting their ability to pay fighters and hire recruits," said Carter, adding that the US-led coalition was "systematically eliminating" IS's cabinet.

Carter refused to offer details about the operation against al-Qaduli, whom many analysts consider the extremist group's second-in-command expected to lead the group if its leader Abu Bakr al-Baghdadi was killed or incapacitated.

US TV network CNN on Friday quoted US officials who spoke on condition of anonymity as saying that the US raid was initially intended to capture al-Qaduli alive.

Meanwhile, Carter acknowledged that striking IS leadership was far from sufficient, noting that "leaders can be replaced."

This was not the first time al-Qaduli had been declared dead. The Iraqi Defense Ministry last May announced that a US-led coalition airstrike killed him in northern Iraq, a claim soon dismissed by the Pentagon.

The US Department of Treasury designated al-Qaduli as a specially global terrorist in 2014. In 2015, the US State Department offered a 7 million US dollars reward for information on him, the highest reward for any IS member except for the group's leader al-Baghdadi.