The second bomb went off after people had gathered to held the victims of the first explosion.

Most Shiites typically make pilgrimages to Karbala, where imam is buried, and millions of people from across Iraq and from other Muslim countries visit for the religious event, which has been the target of sectarian attacks in previous years.

In the northern province of Salahuddin on Monday, five suicide bombers attacked a police station, killing eight officers and wounding 10. The attack began with two of the bombers detonating their explosives at the gates of the station. Three other attackers clashed with security forces inside and were killed, the police said.

After the attack on the station, a suicide bomber blew himself up at the entrance of the local city council in Tikrit, killing a civilian and allowing two other suicide bombers to storm into the building, where they took 42 people hostage. Counterterrorism forces killed the two suicide bombers, freeing the hostages, said an official with the force, Sabah Noori, in a telephone interview. A second civilian was killed during the clashes to free the hostages.

A series of other attacks in Iraq brought Monday’s death toll to 71. In central Baghdad near the Provincial Council building, a car bomb killed six people and wounded 15 others, according to the police. Another car bomb in a Shiite neighborhood in the southwest of the capital blew up in a parking garage, killing six civilians and wounding 14, the police said.

Five people were killed and eight were wounded by a car bomb near the entrance to the Interior Ministry, and a roadside bomb near a public market killed four people and wounded 10, the authorities said.