Passengers flying directly to Britain from Egypt, Jordan, Lebanon, Saudi Arabia, Tunisia and Turkey will be banned from taking laptops and tablet computers into the plane cabin, the British government announced Tuesday.

“Our top priority will always be to maintain the safety of British nationals,” a government spokesman said after the US imposed a similar ban, warning that extremists plan to target planes with bombs in electronic devices.

The US government, citing unspecified threats, had previously barred passengers on nonstop, US-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 smartphones in the passenger cabins, senior Trump administration officials said. Larger electronic items must be checked.

The rules took effect early Tuesday morning and airlines will have until 3am 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, Egypt; Istanbul, Turkey; 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 US-based airlines have nonstop flights from those cities to the United States.

With the order affecting flights from predominantly Muslim nations, the ban may invite comparisons to Trump's orders barring travel from several Muslim-majority-nations, which has been blocked by courts.

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.

The equipment 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.