A laptop ban affecting airline passengers travelling to the UK from six countries in the Middle East and north America is to be introduced "in the coming days", Downing Street confirmed.
The restriction - which means customers will no longer be able to carry laptops and other large electronic devices as cabin luggage - affects passengers on inbound flights from Turkey, Lebanon, Jordan, Egypt, Tunisia and Saudi Arabia.
See also: Brits to be banned from taking laptops on Middle Eastern flights
See also: US bans laptops on flights from 13 countries
It will cover devices which are larger than a typical smartphone measuring 16cm by 9.3cm by 1.5cm, which will now have to go in the plane's hold.
The move was ordered by Prime Minister Theresa May on Tuesday in the latest of a series of meetings on aviation security, although it was not immediately clear whether the move was introduced in response to a general terror threat or a specific attack from the likes of al Qaida.
Affected airlines were informed immediately, but may take a few days to implement the new security measure, said Number 10.
It follows a similar measure announced on Tuesday by the US authorities affecting flights originating in a longer list of eight mainly Muslim countries.
A Number 10 spokesman said no date had been set for the ban to be introduced, but said it would happen soon.
UK airlines operating direct flights which will be hit by the new measures are British Airways, easyJet, Jet2.com, Monarch, Thomas Cook and Thomson, while overseas airlines affected are Turkish Airlines, Pegasus Airways, Atlas-Global Airlines, Middle East Airlines, EgyptAir, Royal Jordanian, Tunis Air and Saudia.
Devices including Kindles and other e-readers will be banned from the cabin, along with hybrid devices such as the Microsoft Surface and iPad Pro, as well as the new Nintendo Switch gaming system.
Some travellers will be forced to pay extra fees for a checked bag if they want to use these gadgets at their destination.
Most smartphones, including the iPhone 7 Plus and Samsung Galaxy S7, will still be eligible to travel in cabin baggage.
Travel trade organisation Abta warned that laptops and tablets are not typically covered by travel insurance policies for loss, damage or theft if they are placed in the hold.
A spokeswoman for the organisation said: "Passengers travelling to the countries affected may wish to consider leaving their electronic devices at home, although this may be difficult for many, especially business travellers and families travelling with children."
Transport Secretary Chris Grayling said: "We understand the frustration that these measures may cause and we are working with the aviation industry to minimise any impact."
The tightening of security comes just weeks after it was revealed that UK security services have foiled 13 potential attacks in less than four years, while counter-terrorism units are running more than 500 investigations at any time.
Last year the insurgent group al-Shabaab smuggled an explosive-filled laptop on a flight out of Mogadishu, blowing a hole in the side of the plane.