Terror Attack In Britain Is 'Highly Likely'

The threat to the UK from international terrorism has been raised from substantial to severe - meaning an attack is "highly likely".

Announcing the move last night, Home Secretary Alan Johnson said although the threat had increased there was no intelligence to suggest an attack was imminent.

But he urged people to be vigilant.

He added it was not specifically linked to the Christmas Day plane bomb plot or any other incident.

Mr Johnson said: "The Joint Terrorism Analysis Centre (JTAC) has...raised the threat to the UK from international terrorism from substantial to severe.

"This means that a terrorist attack is highly likely, but I should stress that there is no intelligence to suggest than an attack is imminent.

"JTAC keeps the threat level under constant review and makes its judgments based on a broad range of factors, including the intent and capabilities of international terrorist groups in the UK and overseas."

He added: "The highest security alert is critical and that means an attack is imminent, and we are not at that level."

The minister said more measures had been taken to protect aviation since the alleged failed bomb attack on a plane over Detroit at Christmas.

"We have a very adept and very focused counter-terrorism facility in this country and people should be reassured by that," Mr Johnson said.

The Christmas Day bomb plot has moved the focus of the fight against terror onto Yemen.

Suspect Umar Farouk Abdul Mutallab has reportedly claimed he was supplied with explosives there.

Following the attack, the Yemeni government has stepped up a US-backed military operation against al Qaeda sympathisers based in remote areas.

And Prime Minister Gordon Brown has called an international counter-terrorism meeting on Yemen in London for January 27.

A security review conducted in the wake of the failed attack led to Mr Brown's announcement on Wednesday of new measures.

They included a suspension of direct flights between the UK and Yemen and a "no-fly list" to prevent people with suspected militant links from travelling to Britain.

Mr Johnson said: "We still face a real and serious threat to the UK from international terrorism, so I would urge the public to remain vigilant and carry on reporting suspicious events to the appropriate authorities."

Yesterday's escalation of the threat level reverses a decision in July last year to downgrade the likelihood of a terror attack from "severe" to "substantial".

JTAC, a unit within MI5, sets the level based on an analysis of intelligence.

The assessment covers potential attacks by al Qaeda or linked extremist groups