WASHINGTON — The U.S. government, citing unspecified threats, is barring passengers on nonstop, U.S.-bound flights from eight mostly Middle Eastern and North African countries from bringing laptops, tablets, electronic games and other devices on board in carry-on bags.

Passengers flying to the United States from 10 airports will be allowed only cellphones and smart phones in the passenger cabins, senior Trump administration officials said. Larger electronic items must be checked.

The rules took effect Tuesday morning and airlines will have until 3 a.m. EDT Saturday to implement them or face being barred from flying to the United States, the officials said.

They said the decision was prompted by “evaluated intelligence” about ongoing potential threats to airplanes bound for the United States. The officials would not discuss the timing of the intelligence or if any particular terror group is thought to be planning an attack.

The Trump administration officials briefed reporters on condition that they not be identified publicly. That was despite President Donald Trump’s repeated insistence that anonymous sources should not be trusted.

The electronics ban affects flights from international airports in Amman, Jordan; Kuwait City, Kuwait; Cairo; Istanbul; Jeddah and Riyadh, Saudi Arabia; Casablanca, Morocco; Doha, Qatar; and Dubai and Abu Dhabi in the United Arab Emirates. About 50 flights a day, all on foreign carriers, will be impacted. The officials said no U.S.-based airlines have nonstop flights from those cities to the United States.