Security has been tightened across all UK airports over US intelligence reports pointing towards a “credible threat” to trans-Atlantic flights being targeted with a new generation “stealth bomb’’.

US officials believe two terror networks in Syria and Yemen have teamed up to target flights bound for America, media reports said here.

UK transport secretary Patrick McLoughlin confirmed the measures, saying they were being taken to protect the public.

The UK government is not giving any details about what these security changes actually are, but they have not ruled out longer queues at security.

The security changes are not expected to cause big delays at Heathrow — one of the busiest hubs for flights to the US, BBC reported.

Other European airports with direct flights to the US are also stepping up security in a move apparently coordinated to minimise alarm.

British Prime Minister David Cameron’s spokesperson said: “There are terror organisations around the world that seek to do the UK, its citizens, citizens of many other countries, including our western allies, harm. We need to always be vigilant to situations that can develop.”

Jeh Johnson, Washington’s homeland security secretary, said that the measures had been taken in response to “the global threat environment’’.

The US had shared “recent and relevant information with our foreign allies”, he said.

“We will work to ensure these necessary steps pose as few disruptions to travellers as possible. We are sharing recent and relevant information with our foreign allies and are consulting the aviation industry. The changes will be made in the upcoming days,” Johnson said in a statement.

However, the actual terrorism threat level in the UK remains the same, at substantial, which is the middle of the five threat levels and means that an attack is a strong possibility.

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