Police say the bomb exploded Sunday evening as the bus was passing by the predominantly Sunni suburb of Saqlawiyah, located 75 kilometers (45 miles) west of Baghdad.

The bus was filled with Pakistani pilgrims who were headed from Syria to the gold-domed shrine to a Shiite imam in the northern Baghdad neighborhood of Kazimiyah.

A medical employee at a nearby hospital says 19 passengers were hurt by the blast, and another five were wounded when the bus overturned.

All officials spoke on condition of anonymity because they were not authorized to talk to reporters.