A road accident in northern Iraq has killed at least 16 people, mostly Shia Iranian pilgrims, as millions of people converge on the holy city of Karbala for Arbaeen, one of the world’s biggest religious gatherings.

The accident between the cities of Dujail and Samarra also injured at least 13 people, state news agency INA reported on Saturday, citing the death toll from Khaled Burhan, director of health services in Salaheddine province.

Burhan did not detail the circumstances of the crash but said most of the dead were visitors from Iran. Those hurt were taken to hospitals, he added.

Two minibuses crashed into each other shortly before midnight on Friday, a medical official in Salaheddine told AFP news agency on condition of anonymity, because he was not authorised to speak to the press.

One of the drivers is believed to have fallen asleep at the wheel, the official said, citing witness accounts. He put the death toll at 18.

This year 2.6 million pilgrims, many from Iran, entered Iraq either by road or air since Arbaeen began, according to figures issued on Friday by the interior ministry.

The gathering marks the end of the 40-day mourning period for the killing of Imam Hussein – Shia Islam’s founding figure and grandson of the Prophet Muhammad. This year it concludes September 6 and 7.

Road accidents killed more than 4,900 people last year in Iraq, an average of 13 per day, according to health ministry data.

Conflict, neglect, and endemic corruption have left oil-rich Iraq’s infrastructure, including roads and bridges, in disrepair. Officials also say speed and mobile phone use while driving contribute to crashes. (Al Jazeera)