A car bombing in a commercial area of Baghdad killed at least 60 people and wounded 100 early Sunday, Iraqi police said of the attack claimed by the Islamic State extremist militia.
The bombing took place in Baghdad's central district of Karada where people were shopping in the run-up to the Eid al-Fitr holiday due next week.
Footage on local broadcasters from the site of the bombing showed charred cars and damaged buildings.
Prime Minister Haider al-Abadi inspected the scene of the attack and vowed revenge, state broadcaster al-Iraqiya reported.
Al-Abadi accused what he called "terrorist gangs" of carrying out the bombing after "they were crushed on the battlefield."
Last month, the Iraqi government announced that it had retaken full control of the mostly Sunni western city of Falluja from Islamic State.
Independent website Alsumaria News reported that al-Abadi quickly left Karada because of locals' anger at the alleged inefficiency of security forces which they blamed for the bombing.
In an online statement circulated by its supporters, Islamic State claimed responsibility for the attack. The group alleged that a suicide bomber targeted a crowd of Shiites.
The statement could not be verified by dpa.
The radical Sunni Islamic State regards Shiite Muslims as heretics.
Elsewhere in Baghdad, nine people were killed and 11 injured in a blast amid conflicting reports about its cause.
Some local media said the blast in a market in the mostly Shiite Shaab district in the north had resulted from a bomb.
The Interior Ministry said that an "accidental fire" erupted in the area, causing a blast inside a store.
In recent months, Iraq, backed by a US-led air alliance, has intensified a military campaign to drive Islamic State from the country's mostly Sunni western and northern areas.
On June 18, government forces started a major attack near Islamic State's northern stronghold of Mosul, which is Iraq's second-largest city.