The Iraqi military and its allies have almost defeated Islamic State in its final and largest Iraqi stronghold of Mosul.
The Popular Mobilization Units - made of predominantly Shiite militias - said the remains are believed to be those of civilian prisoners executed by ISIS when it took control of Mosul and surrounding areas in June 2014.
The Baghdad regime recaptured east Mosul earlier this year and are now battling to retake the western side of the Euphrates river from ISIS, which seized the country's second city along with swathes of other territory in 2014.
Iraqi forces aim to dislodge Islamic State militants from west Mosul within a month, despite gruelling urban combat in densely populated terrain, the head of the elite Counter Terrorism Service (CTS) told Reuters on Thursday.
Jonah's mosque was blown up in July 2014, but experts surveying the damage after it was recaptured in January by a USA -backed Iraqi campaign found a network of tunnels dug by the militants, leading down to a 7th century BC Assyrian palace.
Saadi said CTS forces were battling IS inside the Mosul al-Jadida and Al-Aghawat areas in west Mosul on March 12.
The IS is alleged to have killed up to 600 inmates, a lot of them Shia Muslims, when it seized Mosul in 2014.
The few families remaining in the nearby Dawasa district said the militants had set some of their homes on fire as security forces advanced and that the terrorists had fought among themselves.
It is thought there may be as many as 600,000 civilians still trapped in IS-controlled areas of Mosul. Since then, more than 200,000 residents have fled the city, with 65,000 fleeing in just the past two weeks as fighting there has intensified, according to numbers from the International Organization for Migration.
ISIS thugs holding the Iraqi city of Mosul hostage have been warned they are days away from being wiped out by advancing coalition liberators.
A total of 150 women were freed from the Daesh terror organization as Iraqi security forces recaptured a factory in one of Mosul city's western neighborhoods.
The efforts to avoid damaging some antiquities contrast with the destruction of ancient sites across Islamic State's self-declared caliphate in Syria and Iraq, from the desert city of Palmyra to the Assyrian capital of Nimrud, south of Mosul. ISIS has also built a complex system of tunnels and bunkers, and no doubt will unleash even more suicide auto bombs as Iraqi forces move in.
ISIS overran Mosul in the summer of 2014 and swept across large swaths of the country's north and west.