A car bomb has exploded in the central Iraqi city of Najaf, killing at least 13 people, police have said.
The suicide bomber triggered the explosion at a police checkpoint in Maydan Square, near Najaf's Old City.
Dozens of people were reported injured in the attack, which took place near a market as it filled with shoppers.
Najaf is a place of pilgrimage for Shia Muslims, the site of the mausoleum of Imam Ali and the home of several important clerics.
Ayatollah Ali al-Sistani and radical Shia cleric Moqtada al-Sadr are based in the city, some 100 miles (160km) south of the capital Baghdad.
Police officers were among those killed in the attack, which happened as they were searching a vehicle for explosives, Reuters reports.
Najaf governor Assaad Abu Gilel said the dead included seven officers, three women and three children.
He said: "This was a terrorist operation. The police checkpoint prevented the car from entering the Old City, so the terrorist blew himself on the spot."
With some major exceptions, Najaf has been spared the worst of the violence raging elsewhere in Iraq.
But with US and Iraqi forces launching a major security crackdown on Baghdad, there had been speculation that militants would target other areas where security was less tight.