The first explosion killed Shiite religious observers on a bus . The second attack occurred outside a hospital treating victims of the first attack . Motorcycles were used in both attacks , say officials . A bombing in Karachi in late September , during Ashura , killed more than 100 people .
The first explosion targeted Shiite religious observers on a bus . The second attack occurred outside a hospital treating victims of the first blast . Motorcycles were used in both attacks , say officials . A blast in Karachi in late December , during Ashura , killed more than 40 people .