A large blast was heard in Islamabad this morning and Dawn News television channel said the explosion was in a police barracks in the Pakistani capital.
"We have heard a huge explosion. We are trying to find out the cause," a police official said.'
Security in the city has been stepped in the wake of a suicide truck bomb that killed 55 people and destroyed the Marriott hotel on September 20. There are fears of more bomb attacks in reaction to an army offensive against Islamist militant strongholds in the tribal areas bordering Afghanistan.