The ban, to apply to non-stop U.S.-bound flights from 10 Middle East international airports, will affect nine airlines in total.

The U.S. government is temporarily barring passengers on certain flights originating in eight countries from bringing laptops, iPads, cameras and most other electronic items in carry-on luggage starting Tuesday.

The reason for the ban was not immediately clear. U.S. security officials would not comment.

The ban was revealed on Monday in statements from the Royal Jordanian Airlines and the official news agency of Saudi Arabia.

A U.S. official told the Associated Press that the ban will apply to non-stop flights to the U.S. from 10 international airports serving Cairo, Amman, Kuwait City, Casablanca, Doha, Riyadh, Jeddah, Istanbul, Abu Dhabi and Dubai.

Another U.S. official said the ban would affect nine airlines in total, and the Transportation Security Administration would inform the affected airlines on Tuesday.

The officials, not authorised to disclose the details of the ban ahead of a public announcement,spoke on the condition of anonymity.

The Royal Jordanian Airlines said cellphones and medical devices were excluded from the ban. Everything else, it said, would need to be packed in checked luggage. The ban affects its flights to New York, Chicago, Detroit and Montreal.

David Lapan, a spokesman of the Homeland Security Department, declined to comment. The Transportation Security Administration, part of Homeland Security, also declined to comment.

A U.S. government official said such a ban was considered for several weeks.

The ban would begin just before Wednesday’s meeting of the U.S.-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 Rand Corp., said the nature of the security measure suggested that it was driven by intelligence of a possible attack. He added that 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 the Metropolitan State University of Denver, said there were disadvantages to having everyone put their electronics in checked baggage. Thefts from baggage would skyrocket, as when Britain 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 U.S. 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.