Rachid Kassim is believed to have guided half of the 17 terrorist attacks against France in 2016.
Recovered documents contain photographs of fighters along with their names and personal information.
Bodies covered in bullet holes and flies are left on streets to send intimidating message.
Iraqi army has regained control of the city's east and is now ready to push across the Tigris.
Kurdish media reported that the jihadi was killed by 'unknown gunmen' in northern Iraq stronghold
Analysts say Islamic State's child soldiers are intended to scare the world.
Iraqi PM Haider al-Abadi praises 'heroism' of troops after Isis 'collapse' in Mosul.
The jihadist group is said to have beefed up security to prevent further escapes.
UN has warned 750,000 are in direct danger as the Iraqi army prepares its assault on Mosul.
Security sources in Mosul confirmed Abu Abdel Rahman, a Saudi leader, was in charge of executing women.
Iraqi soldiers in eastern Mosul have celebrated victory by pausing for selfies with Daesh corpses.
The US-led coalition also continued air strikes in Iraq and Syria against the Islamic State group.
The air strike targeted Abu Ibrahim al-Tunsi, a Tunisian jihadist in Idlib governorate.
Iraqi forces recaptured the eastern half of the nation's second city and are now eyeing the west.
As Iraqi forces push Isis out of Mosul, IBTimesUK looks at the impact on southern Iraq
Peter Cook said the counter-Isis campaign is continuing to target senior leaders, including chief Abu Bakr al-Baghdadi.
The Iraqi government recently said it had so far liberated 70% to 80% of east Mosul from Isis.
The battle to retake Iraq's second city from Isis could be complete within three months.
The US military said there was no indication the hospital had been used as a medical facility for some time.
Navy Capt Jeff Davis said there are signs of weakness and low morale among the Islamist militants fighting in Mosul.
Troops captured al-Muthana in the city's east after fighting and at least 19 air strikes.
The execution comes as Iraqi forces intensify their offensive against Daesh fighters to liberate Mosul.