Haider al-Abadi's order came after the UN demanded an inquiry into the alleged atrocities.
Iraq's prime minister on Monday ordered an investigation into violations of human rights and other abuses purportedly committed by government troops and paramilitary forces battling the ISIS group to retake the city of Mosul. Haider al-Abadi said the probe will examine "cases of kidnappings, mistreatment and violations" against civilians. Mr Al-Abadi blamed such incidents on "groups that exploit the good name" of Iraqi soldiers and Shia and Sunni paramilitaries.
The statement also said that the abuses were recorded and then posted on social media to "spoil the joy of victory and to defame the real image of the brave security forces and their sacrifices to liberate the land and to maintain security."
Mr Al-Abadi's statement came days after the UN demanded a government probe into a video purportedly showing brutal treatment and killing of at least three ISIS suspects in a newly-taken area in eastern Mosul.
The nearly three-minute video showed members of the security forces in regular army and police uniforms dragging and beating the suspects in a residential area before showering them with bullets as at least two army Humvees, a tank and a personnel carrier were stationed nearby.
Iraqi and Kurdish forces launched the massive operation in October to retake Mosul, which fell to ISIS in the summer of 2014. The US is supporting them with airstrikes, and US soldiers are serving in a support role on the ground. Paramilitary troops are also taking part in the operation, but only in areas surrounding Mosul.
The push to retake Mosul is the biggest military operation in Iraq since American troops left in 2011 and, if successful, would be the strongest blow yet to ISIS.