A suicide bomber hit a crowded tent full of people in a market in Baghdad on Saturday, killing at least 32 people.

The attack targeted Shiite Muslims participating in Ashura, the annual ritual which commemorates the killing of Imam Hussein, the grandson of the Prophet Muhammad, as Reuters reports.

The Islamic State group claimed responsibility for the attack, according to multiple reports.

This comes as the Iraqi military prepares to launch an offensive to retake the key city Mosul, the only urban center in the country still under Islamic State control. It will be the "largest mission Iraqi security forces have yet undertaken against the enemy," according to the spokesman for the U.S.-led coalition.

The tent hit by the bomber was in northern Baghdad, and authorities told Reuters that "some people were also in the tent to mourn the death of a local resident."

Hussein Khazem, who owns a clothing warehouse in the area, told The Associated Press that the he "saw a large number of killed and wounded people, many burning cars and major damage to the local market."

Baghdad sees regular bombings, including a deadly truck bomb in the Karradah neighborhood that killed more than 300 people in July. That attack was the "deadliest single attack in Iraq since the U.S.-led invasion that toppled Saddam Hussein in 2003," as Reuters reported.

Copyright 2016 NPR. To see more, visit http://www.npr.org/.