The United Kingdom is one of a number of countries stepping up security procedures at some airports, a UK transport official has told the BBC.

It follows an announcement by US homeland security that it will put "enhanced security measures" in place in certain overseas airports with direct flights to the US.

The move comes amid US media reports that al-Qaeda affiliates in Syria and Yemen are developing bombs to smuggle on planes.

Transport correspondent Richard Westcott says the details on what the new security measures will involve and which airports and flights are involved are being kept quiet.