A car bomb exploded in a crowded street in a city north of the Iraqi capital on Saturday, killing 12 people and wounding 13, police and a doctor said.
The blast in Samarra came as people shopped ahead of Eid al-Adha, the Feast of Sacrifice, which begins on Tuesday.
It is the biggest Muslim holiday of the year.
Militants seeking to cause maximum casualties frequently bomb places in Iraq where crowds of people gather, including shopping districts, markets, cafes and mosques.
Violence in the country has reached a level not seen since 2008, when Iraq was just emerging from a brutal sectarian conflict.
This year's spike in violence, which has included a number of sectarian attacks, has raised fears of a relapse into the kind of intense Sunni-Shiite bloodshed that peaked in 2006-2007 and killed tens of thousands of people.
The latest unrest takes the number of people killed so far this month to more than 270, and to over 4,950 since the beginning of the year, according to AFP figures based on security and medical sources.