Three senior ISIS leaders have been killed in US-led airstrikes in Iraq, a US defense official reported Thursday. According to Joint Chiefs of Staff chairman Gen. Martin Dempsey, the airstrikes were launched to impede the Islamic State's ability to conduct its own attacks, supply its fighters and finance its operations.

At least three prime ISIS leaders have been killed in the recent US airstrikes in Iraq, Gen. Dempsey disclosed in an interview with the Wall Street Journal.  The leaders' deaths were result of operations launched in the past month and a half, which are part of an intensifying coalition effort ahead of a planned 2015 offensive.

"It is disruptive to their planning and command and control," Gen. Dempsey said. "These are high-value targets, senior leadership."

Based on the general's report, ISIS leader Abu Bakr al-Baghdadi's deputy Haji Mutazz and ISIS' top military commander Abd al-Basit were killed during the US airstrikes launched between Dec. 3 and 9 while mid-level commander Radwin Talib was killed in an attack carried out late November. As per The Independent UK, Gen. Dempsey revealed that Talib was in control of Iraq's second city Mosul.

An American intelligence source revealed that Mutaaz, also known as Fadel Ahmad Abdullah al-Hiyali, was a very high-ranking and vital figure of ISIS especially in Iraq. CBS News reported Mutaaz, who was a former lieutenant colonel in Saddam Hussein's Special Forces, supervised the governance of Iraqi provinces under Islamic State's control and was recently given the title of Governor of Deir Azzour province in Syria.

Though the deaths of ISIS leaders Mutazz and al Basit, who were killed by the airstrikes launched by the US, were considered a serious blow to the Islamic State's command and control, NBC News reported a defense official said it will be just a temporary setback since the terrorist group has plenty of willing replacements.

The news that ISIS leaders were killed by US airstrikes came the same day the chief US commander of coalition efforts against the Islamic State, Lieutenant General James Terry, commended the impact of the four months offensive operations in Iraq, Yahoo! News UK reported.

"We've made significant progress in halting that (militant) offensive," Terry said.

Despite the deaths of the three top-key ISIS leaders, who were killed by the US-led airstrikes, Terry said it would still be a long battle to defeat the ISIS militants. He also warned that it will take several years to build capabilities of Iraqi forces, who crumbled during ISIS' attacks this summer. As of Thursday, US had conducted 1,361 airstrikes, many of which in support of Iraqi forces.