At least one person has been killed and three injured in an explosion in the car park of Islamabad's international airport, Pakistani police say.
At least one person was killed in the blast
A senior officer told the BBC the blast occurred after a group of armed men was challenged by security guards.
Three of the attackers were injured in an exchange of fire. One tried to throw a grenade, but died when it exploded.
Police suspect he was a suicide bomber and are examining whether he was carrying more explosives.
Officials said at least one suspected accomplice was arrested.
Series of bombings
The BBC's Barbara Plett in Islamabad says the significance of this bombing is more the target than the human loss.
The international airport serves the capital and is used by many foreigners and dignitaries. Last month, a suicide bomber attacked a five-star hotel in Islamabad.
The attacks are the latest in a series of bombings in different parts of the country over the past two weeks that have killed more than 20 people.
Unofficially, police are saying they could be connected to militant tribesmen in the border region near Afghanistan, our correspondent says.
Militants had threatened to take revenge for recent army air strikes there.