Airports across Yorkshire have stepped up security measures just three days after the US announced that terrorists in Syria and Yemen may have been developing explosives that could be smuggled onto planes.

The new measures had affected major airports, which flew directly to the US yet now it seems the extra precautions are also being taken at smaller locations.

Passengers carrying a mobile phone or tablet device will have to show that it can turn on otherwise it will not be allowed on the flight.

An initial warning had been released last week after US security chiefs told Britain’s Department for Transport (DfT) that al-Qaida operatives in the two aforementioned countries had joined forces to develop bombs that would avoid detection and bring down aircraft.

A spokeswoman for Britain’s transport ministry declined to give any further details on any further security measures or to say whether the increased security was even linked to the US concerns.

Meanwhile, a US Department of Homeland Security (DHS) official said the changes were a response to a ‘real time’ and ‘credible’ threat but could not comment on specific intelligence matters.

“Aviation remains an attractive target to global terrorists, who are consistently looking for ways to circumvent our aviation security measures,” the spokesperson said.

“As always, DHS continues to adjust security measures to fit an ever evolving threat environment.

“Information about specific enhancements and locations are sensitive as we do not wish to divulge information about specific layers of security to those who would do us harm.”

The main concern is that militant groups could try to blow up US or Europe-bound planes by concealing bombs on foreign fighters carrying Western passports who spent time with Islamist rebel factions in the region, according to the US sources.