ISLAMABAD — A Pakistani police official says a bomb blast in the city of Rawalpindi has killed four people.

Omar Sohail said the blast also wounded 15 people.

He said police are investigating whether it was a suicide bomber on a motorcycle who blew himself up.

Rawalpindi is next to the capital of Islamabad and is home to Pakistan's military headquarters. The explosion happened in an area where there are many military installations.

The blast came one day after 20 troops were killed in northwest Pakistan in one of the deadliest incidents against their forces fighting militants in the tribal regions.

The Pakistani Taliban claimed responsibility for that incident.