LONDON — Britain has followed the U.S. in announcing a ban on large electronic devices in carry-on bags on direct flights to the UK from six countries in the Middle East and North Africa.

The ban is reportedly in response to an unspecified terror threat that may include laptop bombs.

The U.K. ban applies to all electronic devices larger than a normal smartphone, specified as 16 cm x 9.3 cm x 1.5 cm (6.2 inches long x 3.6 inches wide x 0.5 inches thick), the Guardian reported.

Passengers with larger smartphones, and devices such as tablets and laptops must put those items in their checked baggage.

Eight overseas airlines are affected by the U.K. ban: Turkish Airlines (Turkey), Pegasus Airlines (Turkey), Atlas-Global Airlines (Turkey), Middle East Airlines (Lebanon), Egyptair (Egypt), Royal Jordanian (Jordan), Tunis Air (Tunisia) and Saudia (Saudia Arabia).

The ban also affects British carriers British Airways, EasyJet, Jet2, Monarch, Thomas Cook and Thomson.

Passengers who booked cheaper tickets with carry-on baggage only would likely be hit in the pocket, Independent travel editor Simon Calder told BBC News.

Around 1,000 passengers bound for the U.K. transit through Istanbul on Turkish Airlines every day.

Those passengers will also have to check-in larger electronics at their original point of departure, which means some long flights with no iPad, Kindle or laptop for company.