Abu Sayyaf, known for playing a prominent role in ISIS execution and propaganda videos, is thought to have been killed alongside a fellow militant in Nineveh, a city in Iraq which is located on the outskirts of Mosul.
The terrifying ISIS killer is known for his "huge body and heavy arms" and is thought to have decapitated hundreds of victims.
Al-Mallah claimed that unknown gunmen opened fire on Sayyaf's car, adding: "He was killed along with another militant who was accompanying him during the attack.”
Police have not yet identified the men behind the shooting.
Muhammad Yawar, an Iraqi journalist, also confirmed Sayyaf's death.
He said: "Abu Sayyaf was one of the scariest executioners in Nineveh. He was known for his huge body and heavy arms. He was one of the renowned faces in the ISIS propaganda videos,
"Abu Sayyaf was a reflection of the brutality of this terrorist group ."
Sayyaf is the second executioner to be killed recently, after Abu Abdel Rahman was also attacked by unknown gunmen, in the al-Askari region in Iraq.
Last week, Coalition forces were preparing for months of horrific street-to-street fighting in the liberation battle to drive 2,000 diehard Islamic State fighters from the Iraqi city of Mosul .
Thousands of troops and armoured vehicles will storm the west of the city for the final but bloodiest stage of the battle to force ISIS out of Iraq.
It is feared as many as 750,000 terrified civilians are among the IS fighters in west Mosul - all under the threat of being beheaded if they try to flee.