The threat is so severe that security at airports worldwide was today being tightened.
The implant-bomb threat is a response to high-tech security measures which, while inconvenient for passengers, have had a real impact on traditional suicide bombing techniques such as hiding explosives in bags, shoes or underwear to avoid detection.
US Homeland Security has already briefed airlines and shared implant-bomb data with other countries' security services.
Experts believe male bombers would have the explosive inserted near their appendix or in their buttocks.
Female bombers would have the material placed inside their breasts, in the same way cosmetic implants are inserted.
They added that 8oz of the explosive PETN (Pentaerythritol Tetranitrate) would be enough to blow a large hole in an airliner.
The explosives would be detonated by the bomber using a hypodermic syringe to inject TATP (Triacetone Triperoxide) through their skin into the explosives sachet.
The leaked document says: “The Department of Homeland Security has identified a potential threat from terrorists who may be considering surgically implanting explosives or explosive components in humans to conduct terrorist attacks.”