A bomber blew himself up at a police station housing the country's terrorism intelligence offices, killing himself and one officer.
The blast late Monday on Pakistan's national day was the first bombing in the capital, Islamabad, since last September, when more than 50 people were killed in a suicide truck bomb attack on the Marriott Hotel.
Islamist terrorists are blamed for near-daily attacks in the Western-allied but increasingly unstable country, though little information on Monday's bomber was immediately available.
The man detonated explosives at the gate of the police station in the center of the capital, Interior Ministry secretary Kamal Shah said. He said an officer who was apparently challenging the bomber died in the blast.