The US government is from today temporarily barring passengers on certain flights originating in eight other countries from bringing laptops, iPads, cameras and most other electronics in carry-on luggage.
The reason for the ban was not immediately clear.
The ban was revealed on Monday in statements from Royal Jordanian Airlines and the official news agency of Saudi Arabia.
The ban will apply to non-stop flights to the US from 10 international airports serving the cities of Cairo in Egypt; Amman in Jordan; Kuwait City in Kuwait; Casablanca in Morocco; Doha in Qatar; Riyadh and Jeddah in Saudi Arabia; Istanbul in Turkey; and Abu Dhabi and Dubai in the United Arab Emirates, a US official said.
The ban is indefinite.
A second US official said the ban will affect nine airlines in total, and the Transportation Security Administration were to inform the affected airlines early today.
Royal Jordanian said mobile phones and medical devices were excluded from the ban. Everything else, the airline said, would need to be packed in checked luggage.
Royal Jordanian said the electronics ban affects its flights to New York, Chicago, Detroit and Montreal.
A US government official said such a ban has been considered for several weeks.
Homeland Security Secretary John Kelly phoned politicians over the weekend to brief them on aviation security issues that have prompted the impending electronics ban, according to a congressional aide.
The ban would begin just before Wednesday's meeting of the US-led coalition against the Islamic State group in Washington. A number of top Arab officials were expected to attend the State Department gathering.
It was unclear whether their travel plans were related to any increased worry about security threats.
Brian Jenkins, an aviation-security expert at the Rand Corp, said the nature of the security measure suggested it was driven by intelligence of a possible attack.
He added there could be concern about inadequate passenger screening or even conspiracies involving insiders, airport or airline employees, in some countries.
Another aviation-security expert, professor Jeffrey Price of Metropolitan State University of Denver, said there were disadvantages to having everyone put their electronics in checked baggage.
Thefts from baggage would sky-rocket, as when the UK tried a similar ban in 2006, he said, and some laptops have batteries that can catch fire, an event easier to detect in the cabin than in the cargo hold.
Most major airports in the United States have a computer tomography or CT scanner for checked baggage, which creates a detailed picture of a bag's contents.
They can warn an operator of potentially dangerous material, and may provide better security than the X-ray machines used to screen passengers and their carry-on bags.
All checked baggage must be screened for explosives.