Sixteen people, mostly Iranian pilgrims, were killed in a road accident north of the Iraqi capital Baghdad overnight, the state news agency INA reported on Saturday.
The “horrible accident” between Dujail and Samarra also injured 13 people, Khaled Burhan, director of health services in Salaheddine province, said.
Most of the dead were Shiite Muslim pilgrims from Iran, he said, but he did not detail the circumstances of the crash.
Almost exactly a year ago, on September 11, 11 Iranian Shiite pilgrims and their local driver died when their minibus collided with a truck in Babil province, south of Baghdad, a health official said at the time.
Millions of Shiite pilgrims, many of them from Iran, head each year to the holy shrine city of Karbala for Arbaeen, one of the world's biggest religious gatherings.
Arbaeen marks the end of the 40-day mourning period for the killing of Imam Hussein – a founding figure in Shiite Islam and grandson of the Prophet Mohammed – by the forces of the caliph Yazid in 680AD.
More than 2.6 million pilgrims have flown into Iraq or crossed its land borders since Arbaeen began this year, according to figures issued on Friday by Iraq's interior ministry.
Road accidents are a recurring accompaniment to Arbaeen, which concludes September 6-7 this year.
Conflict, neglect and endemic corruption have left oil-rich Iraq's infrastructure, including roads and bridges, in disrepair. Officials also say speed, mobile phone use and driving while impaired contribute to crashes.
Last year in Iraq, road accidents killed more than 4,900 people, an average of 13 per day, according to health ministry data.