At least 31 pilgrims died Tuesday in a stampede at a major shrine in Karbala, Iraq, where they celebrated the holy day of Ashura, the Iraqi health ministry said.
The ministry's spokesman, Saif al-Badr, said the figure could increase further, as another 100 people were injured, including 10 in critical condition.
It is the deadliest stampede in recent history during Ashura, when Shiite pilgrims from around the world swarm Karbala to commemorate Hussein's martyrdom, the grandson of Prophet Muhammed (PBUH).
On Tuesday, processions full of faithful dressed in black headed to their sanctuary with a golden dome in Karbala, carrying black flags with "Hussein" written in red and groaning loudly.
Similar ceremonies took place in the capital Baghdad and in the cities of southern Najaf and Basra.
Under the Sunni-dominated regime of former dictator Saddam Hussein, the vast majority of Ashura's commemorations were banned. Now, the day is a national holiday, with closed streets throughout the country to allow elaborate recreations of the Battle of Karbala.
In 2005, at least 965 pilgrims heading to the Imam Kadhim shrine in Baghdad during a different holiday died after the rumors of a suicide bomber in the crowd caused a massive stampede.