A bomb blew up inside a cafe in the northern Iraqi city of Kirkuk late Friday, killing at least 18 people and wounding 26.
It is unclear if a suicide bomber carried out the attack, and no one has claimed responsibility.
Friday's bombing culminated a violent two days in Iraq that left around 40 people dead.
There appears to be no let up in the violence between Shi'ites and minority Sunnis, which the United Nations says has killed more than 2,500 people since April.
The Associated Press reports Sunni and Shi'ite clerics delivered a joint Ramadan sermon Friday in Baghdad, calling for an end to the violence and a united Iraq.
Iraqi Sunnis complain that the Shi'ite-led government ignores their needs and is marginalizing them politically.