Bombings and shootings targeting Shi’ite Muslim pilgrims in Baghdad and police across Iraq killed at least 53 people on Wednesday in coordinated attacks during a major religious festival.

In the attacks, at least 18 people were killed when four bombs hit pilgrims across Baghdad as they gathered to mark the anniversary of the death of Shi’ite imam Moussa al-Kadhim, a great-grandson of Prophet Mohammad.

One of those blasts killed at least nine people as pilgrims passed through a police checkpoint in central Baghdad.

“A group of pilgrims were walking and passed by a tent offering food and drinks when suddenly a car exploded near them,” said Wathiq Muhana, a policeman whose patrol was stationed near the blast in Karrada district.

“People were running away covered with blood and bodies were scattered on the ground,” he said.

Extra security and checkpoints have been in place this week as thousands of pilgrims arrive in Baghdad to meet at a shrine in the capital’s northern Kadhimiyah district for the Shi’ite religious festival.

Violence in Iraq has eased since the height of the war, but Islamist insurgents tied to al Qaeda are still potent, often targeting Shi’ite pilgrims to try to reignite the sectarian tensions that drove Iraq close to civil war in 2006-2007..