British security agency MI5 has uncovered evidence that the Al Qaeda is planning to insert surgical bombs inside people for the first time and send them over to the country.
Security services believe the move has been prompted by the recent introduction at airports of body scanners, which are designed to catch terrorists before they board flights.
It is understood MI5 became aware of the threat after observing vocal Internet chatter on Arab websites this year.
According to The Independent, the warning comes in the wake of the failed attempt by London-educated Nigerian Umar Farouk Abdulmutallab to blow up an airliner approaching Detroit on Christmas Day.
One security source said: "If the terrorists are talking about this, we need to be ready and do all we can to counter the threat."
Experts said the explosive PETN (pentaerythritol tetranitrate) could be placed in a plastic sachet inside the bomber's body before the wound was stitched up like a normal operation incision and allowed to heal.
Security sources said the bomber would detonate explosives by using a hypodermic syringe to inject TATP (triacetone triperoxide) through their skin into the explosives sachet.