The Takfiri Daesh terrorist group has reportedly executed one of its own commanders along with 57 other members in Iraq’s northern city of Mosul to suppress a “coup” attempt by them in the face of an imminent military operation by the Iraqi government to liberate the city.

Security officials and residents said the slain Daesh members had defected and sought to help Iraqi government forces seize control of the strategic city, which Daesh has declared its so-called headquarters in Iraq.

The attempt was reportedly uncovered last week, and the defectors were killed by drowning. Their bodies were buried in a mass grave in a wasteland on the outskirts of the city.

Hisham al-Hashimi, a consultant to the Baghdad government on the anti-Daesh campaign, said the defectors had been arrested after one of them was caught with a message on his phone mentioning a transfer of weapons. He later confessed that weapons had been hidden in three houses to be used in a rebellion against Daesh and to support the Iraqi army when it launches the offensive on Mosul.

Daesh members later attacked the three locations on October 4 and uncovered the stashes, Hashimi said.

Residents said a list with the names of the 58 executed people was given to a hospital to have their families informed, but their bodies were not returned.

Colonel Ahmed al-Taie, a member of the Nineveh provincial command’s military intelligence, said, “After the failed coup, Daesh withdrew the special identity cards it [had] issued for its local commanders to prevent them from fleeing Mosul with their families.”

People in Mosul, which was overrun by Daesh in 2014, have been expressing their refusal to comply with Daesh’s draconian rule by painting the letter M — which stands for the first letter of the Arabic word that means resistance — on city walls, and the word “wanted” on the walls of the houses of the militants.

Referring to the defections that were nevertheless suppressed, Sabah al-Numani, the Iraqi counter-terrorism service spokesman, said, “This is a clear sign that the terrorist organization has started to lose support not only from the population, but even from its own members.”

The Iraqi army and pro-government forces have been preparing for months for the assault on Daesh in Mosul.