Terror threat: British airports put on alert

Britain's airports were put on alert Thursday amid fears that Islamist groups are working on an undetectable "stealth bomb" which could be implanted inside an extremist's body to bring down an airliner.

Heightened precautions were brought in at terminals around the country since Thursday morning after reports that two terror networks were trying to produce a new explosive, which may have already been tested by militants in Syria, the Daily Mail reported.

It is feared that the groups may be putting together a "non-metallic" device, which could potentially be surgically-implanted inside a terrorist's body and would be almost invisible to current security checks, the report said.

British Prime Minister David Cameron's official spokesman said: "There are terror organisations around the world that seek to do the UK, its citizens, citizens of many other countries, including our Western allies, harm. We need to always be vigilant to situations that can develop."

The alert in Britain was issued after US Homeland Security Secretary Jeh Johnson ordered beefed up security at foreign airports from where aircraft fly into the US.