Large smartphones, tablets, and laptops are being banned from the cabin on flights to the UK from Turkey, Lebanon, Egypt, Saudi Arabia, Jordan, and Tunisia.
Under the new arrangements, phones, laptops, and tablets larger than 16cm in length, 9.3cm wide and 1.5cm deep will not be allowed in the cabin on "selected flights" to the UK from the countries affected, the government said. It follows a similar ban announced by US authorities yesterday.
Smartphones will be allowed in the cabin if they are within those dimensions: larger smartphones will also have to go in the hold.
The UK Department for Transport said passengers should check online with their airline for further details and said: "We understand the frustration that these measures may cause and we are working with the aviation industry to minimise any impact. Our top priority will always be to maintain the safety of British nationals."
It added: "These new measures apply to flights into the UK and we are not currently advising against flying to and from those countries."
Transport Secretary Chris Grayling said: "In conjunction with our international partners and the aviation industry, the UK government keeps aviation security under constant review. The UK has some of the most robust aviation security measures in the world and at all times the safety and security of the public is our primary concern. We will not hesitate to put in place measures we believe are necessary, effective and proportionate."
The Department of Homeland Security said the US government is "concerned about terrorists' ongoing interest in targeting commercial aviation."
It said: "Evaluated intelligence indicates that terrorist groups continue to target commercial aviation, to include smuggling explosive devices in various consumer items," and that as a result it was "prudent" to boost security.
The US ban applies to passengers travelling from 10 specific airports. These are the Queen Alia International Airport (AMM), Cairo International Airport (CAI), Ataturk International Airport (IST), King Abdul-Aziz International Airport (JED), King Khalid International Airport (RUH), Kuwait International Airport (KWI), Mohammed V Airport (CMN), Hamad International Airport (DOH), Dubai International Airport (DXB), and Abu Dhabi International Airport (AUH).
The department said electronic devices larger than a smartphone will not be allowed to be carried on board the aircraft in carry-on luggage, although medical devices will be allowed to remain in a passenger's possession after they are screened.
It said the approximate size of a "commonly available smartphone" would be a guideline for passengers. And it said examples of large electronic devices that will not be allowed in the cabin on affected flights include, laptops, tablets, e-readers, cameras, portable DVD players, electronic games larger than a smartphone and travel printers/scanners.
Airlines were notified on 21 March at 8:00 am EDT and have 96 hours to comply.