Britain has raised its international terrorism threat from “substantial” to “severe”, indicating that the authorities consider an attack to be “highly likely”.
The perceived threat from Yemen since the foiled Christmas Day plot to blow up an American airliner could be one factor behind the move.
Cranking up the threat level may also be to bring the UK in line with the US. It comes in a week when Prime Minister Gordon Brown suspended direct flights between Yemen and the UK.
However, the government may be party to intelligence it does not want to reveal.
Alan Johnson, the British Home Secretary, said: “Moving to this different level says yes, we have to be more alert, and it means that an attack has moved to the level of being likely. But we have absolutely no intelligence to suggest it is imminent.”
Britain hosts an international conference on Afghanistan on January 28, which will be attended by US Secretary of State Hillary Clinton, NATO General-Secretary Anders Fogh Rasmussen and UN Secretary-General Ban Ki-moon.
Britain raises terrorism threat alert