ISLAMABAD - Gunmen attacked one of Pakistan's biggest airports in Karachi on Sunday, killing at least five people, police said. 'The old terminal of Karachi airport was attacked by militants,' said a senior police official. Officials in Karachi, Pakistan's commercial hub, said all flights had been diverted. 'All flights destined for Karachi have been diverted to other cities,' said a civil aviation authority spokesman. No one immediately claimed responsibility for the attack. 'Over half a dozen armed men made towards the runway from the backside of the airport,' said a private television channel, quoting a witness.