Washington: Contract workers for the US State Department improperly viewed Democratic presidential candidate Barack Obama's passport records three times year, and act his campaign called "an outrageous breach" of his privacy.

The State Department said it's initial evaluation proved that three workers in separate offices looked at the records out of "imprudent curiosity", and the actions were not politically motivated. The department has requested further investigation into the matter.

Two of the three contract workers were fired as soon as the unauthorised viewing of Obama's files was discovered, while the third has been disciplined but still works for a contractor who has business with the State Department.

Obama's campaign spokesman, Sean McCormack said, "This is an outrageous breach of security and privacy, even from an administration that has shown little regard for either over the last eight years."

Obama learned of the incidents on Thursday on a plane between campaign stops in West Virginia and Oregon. His staff will get a more detailed briefing on Friday from Undersecretary of State Pat Kennedy.