The Transportation Security Administration warned airlines and foreign security agencies on Wednesday that terrorists groups might try to surgically implant bombs under the skins of passengers.

US officials said that intelligence reports don't relate to any direct or imminent threat. Terrorist groups were considering implanting the bombs to try to escape the detection of airport security. Passengers flying to the United States should be prepared for even more stringent security procedures, the TSA said in a statement.

"These measures are designed to be unpredictable, so passengers should not expect to see the same activity at every international airport," said Mr. Nicholas Kimball, TSA spokesman. He confirmed that current methods could not detect plastic explosives under the skin. The TSA has briefed air carrier and foreign partners on the continued interest of terrorists to target aviation.

'Terrorist groups have repeatedly and publicly indicated interest in pursuing ways to further conceal explosives,' A TSA statement said, without confirming the scheme to implant explosives.

A surgically implanted bomb in a human carrier isn't a new threat. British intelligence had issued a similar warning in January 2010. The TSA had acknowledged the reality of such a threat last year but assured the public that even if the bomb is inserted into body cavities the wires connected to the bomb would still be detectable by traditional security measures such as metal detectors.

White House spokesman Carney has confirmed that President Obama has been fully briefed on the possible technique that could be used by terrorists.