Female homicide bombers are being fitted with exploding breast implants which are almost impossible to detect, British spies have reportedly discovered.

The shocking new Al Qaeda tactic involves radical doctors inserting the explosives in women's breasts during plastic surgery — making them "virtually impossible to detect by the usual airport scanning machines."

It is believed the doctors have been trained at some of Britain's leading teaching hospitals before returning to their own countries to perform the surgical procedures.

MI5 has also discovered that extremists are inserting the explosives into the buttocks of some male bombers.

"Women suicide bombers recruited by Al Qaeda are known to have had the explosives inserted in their breasts under techniques similar to breast enhancing surgery," Terrorist expert Joseph Farah claims.

The lethal explosives called PETN are inserted inside plastic shapes during the operation, before the breast is then sewn up.

The discovery of these methods was made after London-educated Nigerian Umar Farouk Abdulmutallab came close to blowing up an airliner in the U.S. on Christmas Day.

He had stuffed explosives inside his underpants.

Hours after he had failed, Britain's intelligence services began to pick up "chatter" emanating from Pakistan and Yemen that alerted MI5 to the creation of the lethal implants.

A hand-picked team investigated the threat which was described as "one that can circumvent our defense."

Top surgeons have confirmed the feasibility of the explosive implants.

Explosive experts allegedly told MI5 that a sachet containing as little as five ounces of PETN could blow "a considerable hole" in an airline's skin, causing it to crash.

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