A car bomb killed at least 100 people in the town Khan Bani Saad on Friday as Muslims were celebrating the first day of a religious holiday, Eid al-Fitr, police and medical sources said.
Eid al-Fitr is an Islamic holiday marking the end of the holy month of Ramadan. Friday’s attack added to anger among Iraqis as they wished to shun bad memories for at least a few days.
The blast took place in an open market in the town, part of the Diyala province, about 30 km northeast of Baghdad.
Another 50 people were wounded by the blast, which smashed the windows in the area.
Officials fear the figures could increase as operations still continue to rescue the bodies under the debris.
A three-day mourning has been declared by the Diyala province and all parks and entertainment places have been shut down for two days in a bid to prevent further attacks.
Iraqi government is seeking to restore security as its armed forces fight against ISIS.
In a message published on Twitter, ISIS has claimed responsibility for the latest attack, saying the car was carrying three tonnes of explosives.
ISIS has recently stepped up its suicide attacks in and around Baghdad, claiming dozens of lives.
The militant group seized Mosul, Iraq’s second largest city, in June 2014, in a lightning advance that saw Iraqi troops flee leaving military equipments and armoured vehicles behind.
The United Nations says at least 15,000 civilians were killed across Iraq between January 2014 and April 2015.