Amnesty International on Tuesday called for a commission to investigate crimes against civilians in Mosul by all sides in the battle to liberate the Iraqi city from jihadists.
"The horrors that the people of Mosul have witnessed and the disregard for human life by all parties to this conflict must not go unpunished," said Lynn Maalouf, director of Middle East research at Amnesty International.
"An independent commission must immediately be established, tasked with ensuring that any instances where there is credible evidence that violations of international law took place, effective investigations are carried out, and the findings made public."
Iraq on Sunday declared it had successfully ousted ISIL from Mosul, from where the jihadists had declared their self-styled caliphate in 2014.
But the victory has left thousands dead and wounded, and the city has been devastated by the fighting since Iraqi forces launched their offensive in October to retake Mosul.
In documenting the conflict between January and mid-May, Amnesty found ISIL violated international humanitarian law and committed war crimes.
The jihadist group used civilians as "human shields" and "summarily killed hundreds, if not thousands" of people as they tried to flee, hanging victims' bodies in public places, Amnesty said.
The human rights organisation also criticised Iraqi forces and the US-led coalition, stating they carried out "a series of unlawful attacks" in the city.
Pro-government forces used "imprecise, explosive weapons" in the urban conflict and allegedly used disproportionate force, such as a March 17 attack cited by Amnesty in which 105 civilians died in an air strike targeting two ISIL snipers.
"Iraqi and coalition forces failed to take adequate measures to protect civilians, instead subjecting them to a terrifying barrage of fire from weapons that should never be used in densely populated civilian areas," Ms Maalouf said.
In addition to calling for an independent commission, Amnesty published a series of recommendations for the Iraqi authorities including establishing a compensation programme for civilians.