Militants have carried out a number of attacks on cafes in recent weeks, especially during the Muslim holy month of Ramadan, when many Iraqis went to cafes after breaking their daytime fast.
This Ramadan, which ended last week, was one of the deadliest for Iraq in years, with more than 800 people killed in attacks.
The bomber struck a cafe in the town of Balad at around 6:30 pm (1530 GMT) on Monday, also wounding more than 35 people, municipal council chief Faris Jaafar said.
The attack came a day after Al-Qaeda front group the Islamic State of Iraq and the Levant claimed attacks that killed more than 70 people on Saturday.
"The Islamic State mobilized... in Baghdad and the southern states and others to convey a quick message of deterrence on the third day of Eid al-Fitr," the group said.
The attack also came just weeks after assaults on prisons near Baghdad, also claimed by the Al-Qaeda front group, freed hundreds of prisoners including leading militants.
The brazen assaults highlighted both the growing reach of militants in Iraq, as well as the rapidly worsening security situation.
With the latest violence, attacks in Iraq have killed 3,396 people since the beginning of the year, according to figures compiled by AFP -- an average of 15 people killed each day.
NJF/NJF