Britain lowers al Qaeda threat level

LONDON (Reuters) - Britain Monday downgraded the threat from international terrorism to "substantial," the third highest on a five-point scale, from "severe," but said there was still a strong possibility of an attack.

Authorities define the international terrorist threat as stemming from diverse groups include al Qaeda, associated networks, and those who share its ideology but have no direct contact with it.

"We still face a real and serious threat from terrorists and the public will notice little difference in the security measures that are in place, and I urge the public to remain vigilant," Home Secretary Alan Johnson said in a statement.

"The police and security services are continuing in their thorough efforts to discover, track and disrupt terrorist activity," he added.

The Joint Terrorism Analysis Centre lowered the threat level based on factors including the intent and capabilities of international terrorist groups in Britain. It gave no further details.

Groups inspired by al Qaeda are classified as international terrorism while dissident Irish republicans come under the bracket of domestic terrorism.

In July 2005, four British Muslims blew themselves up on London underground trains and a bus, killing 52 people and wounding 700.

The current alert system was introduced in 2006 and the threat level has been at "severe" for most of the past three years, meaning an attack was considered highly likely.

The authorities have twice raised it to the highest level, "critical," meaning an attack is expected imminently.