Air strikes kill IS group leaders in Iraq

Several Islamic State group leaders have been killed in US air strikes in northern Iraq in recent weeks, a US defence official says.

"These were the result of a series of air strikes this month carried out over several days," the official told news agency AFP on Thursday on condition of anonymity.

"We've long said command and control, including leadership, remain valid targets."

The strikes were part of "degrading" IS's ability to command and control their forces, the official said.

The operation was described as "not insignificant" and reflected a wider effort to pressure the group as Iraqi forces prepare for a major counteroffensive in the coming months.

The jihadist leaders killed did not include chief Abu Bakr al-Baghdadi.

The Wall Street Journal first reported US forces had taken out several key leaders, quoting top officer, General Martin Dempsey.

"These are high-value targets, senior leadership," Dempsey told the Journal.

The newspaper, quoting unnamed officials, said between December 3 to December 9, air raids killed a man known as Abd al-Basit, the head of the group's military operations in Iraq, and Haji Mutazz, a deputy to Baghdadi, the IS chief.

A third figure, Radwin Talib, the IS group's leader overseeing the city of Mosul, was killed in a strike in late November.