AIR passengers flying to the United States will have electronic equipment such as tablets and smartphones confiscated unless they can prove the devices switch on, under tougher security measures.

The US Transportation Security Administration (TSA) has announced it will not allow uncharged electronic devices on to US-bound airplanes at some overseas airports, including London Heathrow.

The TSA said passengers at certain international airports may be asked during security screening to turn on electronic devices to prove that they are not carrying dummy equipment.

Tablets, laptops and mobile phones already have to pass through security screening but can be turned off. Now, if an owner cannot power them up when asked, they will not be allowed to carry them on to the plane.

The latest measure comes days after enhanced security checks were brought in across the board amid suggestions of a plot by Islamic extremists to blow up an airliner, possibly using explosives implanted inside a suicide bomber's body.