It is the latest setback for the jihadists who have also lost territory in neighbouring Syria and in Libya in recent weeks
Around 100 NZDF personnel and 300 Australian Defence Force troops are involved in the mission at Camp Taji
Police of Anbar said the mass burial site was discovered in the town of Saqlawiya, northwest of Fallujah in the Euphrates Valley
Prime Minister has ordered the creation of a human rights committee to examine violation to the instructions on the protection of civilians
Attacks by ISIS come as Iraqi forces are attempting to retake the western city of Fallujah from Islamic State militants
Fighting also raged hundreds of kilometres further up the Euphrates Valley in Syria
The Iraqi army said in late March that its troops had launched what was expected to be a long offensive to retake Mosul
According to the government, ISIS controls only 14% of Iraqi territory, down from the 40% it held in 2014
The US further added that it can only provide a training and advisory role in the war-torn nation, after it emerged that ISIS had killed a third American soldier
ISIS has claimed responsibility for the attack
A doctor at Hilla hospital said at least 11 of the wounded were in a very serious condition
The last month saw significant deterioration in Iraq's security situation
According to a UN report, over 22,300 people were either killed or injured in armed conflict in 2015.