A senior ISIS commander has been killed in the battle for Mosul

A senior ISIS commander has been killed in the battle for Mosul, the terror group's last major stronghold in Iraq, Iraqi military intelligence sources tell CNN.

Mahmoud Shukri al Nuaimi, a senior figure in the militant setup who also is known as Sheikh Faris, was killed Tuesday in an Iraqi-led coalition airstrike in western Mosul, the sources said.

ISIS confirmed his death in a video montage, referring to him as "the martyr of the battle."

ISIS shot and killed 40 civilians Tuesday in Mosul after accusing them of "treason and collaboration" with Iraqi security forces, according to a report released Friday by the Office of the UN High Commissioner for Refugees.

"The victims were dressed in orange clothes marked in red with the words: 'traitors and agents of the ISF.' Their bodies were then hung on electrical poles in several areas in Mosul city," the report said.

The United Nations said a 27-year-old man was reportedly publicly shot to death Tuesday evening in central Mosul's Bab al-Jideed neighborhood for using a mobile phone.

On Wednesday evening, ISIS reportedly killed 20 civilians at the Ghabat military base in northern Mosul on charges of leaking information, the UN body said. "Their bodies were also hung at various intersections in Mosul, with notes stating: 'decision of execution' and 'used cell phones to leak information to the ISF.' "

The UN report tallies with what witnesses have told CNN.

Iraqi military intelligence sources told CNN that ISIS executed seven men, whom they had accused of spying for the Iraqi military, in the western part of the city. The men, who were dressed in orange jumpsuits, were the latest victims of an ongoing campaign of terror by the militant group in Mosul.

Jihadists have been killing suspected Iraqi security forces collaborators since Monday, witnesses said. All the victims have been male, the witnesses said, and have been shot in the head.

Some witnesses said dozens of bodies are being left at intersections across the city -- stark warnings to residents not to collaborate with the incoming Iraqi forces. They are not being removed as residents fear reprisals from ISIS militants.

The corpses have been seen in areas on both sides of the city, among them the Zuhur and Karama neighborhoods in the east, and the old city on the west side of the Tigris River.