The suspects were nabbed during a search operation when the security personnel stopped a vehicle with fake registration number, a Press TV correspondent reported on Sunday from Islamabad.
Police sources said that heavy explosives and ammunition were also recovered from the suspects.
The bombers were reportedly planning to target key installations and government buildings in the city.
The developments come hours after a suicide bomber attacked a police emergency response unit in downtown Islamabad, killing at least two policemen and injuring several others.
Islamabad and other major cities across Pakistan have been braced for suicide attacks since the army launched an offensive against the insurgents in the troubled northwestern Swat valley and its adjoining districts in early May.
Bomb attacks blamed on insurgents have killed more than 1,900 people across the country in the past two years
