Blast kills 23 in Pakistan

(CNN) - A blast at a hospital in northwest Pakistan killed at least 23 people Tuesday, authorities said. Another 15 to 20 were injured.

The explosion occurred near the emergency entrance to the Dera Ismail Khan District Hospital, said Malik Naveed, inspector general of police for the North West Frontier Province, where the district is located.

The bomb went off while a crowd gathered outside the hospital to protest the shooting death of a Shi'ite Muslim leader, Naveed said.