The United States does not handle the passenger screening on American-bound flights from overseas. But foreign airports have to meet a series of requirements from the Department of Homeland Security and the Transportation Security Administration in checking such passengers before they board.

The new measures apply to some airports in Europe, the Middle East and Africa. Passengers will have to turn on the electronic devices while being screened by security personnel to prove that the devices are harmless, the T.S.A. said Sunday. The fear is that unresponsive phones have been hollowed out and filled with explosives. It is considered next to impossible to detonate such devices at the checkpoints because they require external triggering mechanisms.

If an initial attempt fails to power up a device, passengers will be allowed to use a charger. If that fails, the devices will be confiscated. The T.S.A. said similar screening might be extended to other electronic devices like laptops and tablets. Some countries may also add security measures of their own.

It is not clear what will happen to the confiscated devices.

The T.S.A. did not say how long the new policy would remain in place, nor would it specify the countries or airports that would be affected. Last week, the Department of Homeland Security said that it had called for tightened passenger screening on many United States-bound flights from 15 airports in Europe, Africa and the Middle East, although it did not say which airports.

Since 2009, the Qaeda affiliate in Yemen has unsuccessfully planned at least three attacks on airliners using bombs carried on board or planted in cargo.