WASHINGTON - The National Security Council identified the slain militant as Fadhil Ahmad al-Hayali, also known as Haji Mutaz, and said he was Daesh leader Abu Bakr al-Baghdadi's senior deputy.

This is not the first time that US officials have announced Hayali's death.

In December, US defense officials, speaking to reporters on condition of anonymity, said he was one of several senior figures killed in coalition strikes, giving another of his pseudonyms, Abu Muslim al-Turkmani.

But US forces now say they were able to kill him, along with an Daesh "media operative" known as Abu Abdullah, on August 18 in a strike on a vehicle near the city of Mosul.

The White House described Hayali as a member of the Daesh's ruling council, and "a primary coordinator for moving large amounts of weapons, explosives, vehicles and people between Iraq and Syria".

"He supported Daesh operations in both countries and was in charge of Daesh operations in Iraq, where he was instrumental in planning operations over the past two years, including the Daesh offensive in Mosul in June 2014," it said.

Like many senior Iraqi jihadists, before joining the Daesh group, Hayali had been a member of Al-Qaeda's Iraqi faction.

He was reportedly a former Iraqi officer from the era of Saddam Hussein.

Daesh militants launched a devastating offensive in Iraq in June 2014.( AFP)