BAGHDAD — Iraq’s prime minister says security forces have detained a man suspected of detonating a bomb on a minibus packed with passengers outside the Shiite holy city of Karbala.

The Friday night blast killed 12 people and wounded five others.

Adel Abdul-Mahdi in a statement released by his office Saturday gave no further details about the suspect.

The blast was one of the biggest attacks targeting civilians since the extremist Islamic State group was declared defeated inside Iraq in 2017.

The group’s sleeper cells continue to wage an insurgency and carry out sporadic attacks across the country.

On Saturday security was tight on the roads leading to Karbala with added checkpoints searching cars.