Alert raised for terror attacks on Britain by Irish dissidents

Home Secretary Theresa May announced the increase in the threat assessment after the head of the MI5 warned that dissident Irish republicans could attempt to mount a new wave of terrorist attacks on the British mainland.

But it was still lower than the overall threat to the UK from international terrorism, published by the Joint Terrorism Analysis Centre (Jtac). This remains at severe, meaning an attack is highly likely.

Mrs May said: "The director-general of the Security Service has informed me he has raised the threat to Great Britain from Irish-related terrorism from moderate to substantial, meaning that an attack is a strong possibility. Judgments are based on a broad range of factors, including the intent and capabilities of terrorist groups."

The assessment of the risk posed by Irish-related terrorism was published for the first time "to encourage people to remain vigilant", she said.

Mrs May added: "We have been consistent in stating that the threat to the UK from terrorism is real and serious.

"The balance we aim to strike is keeping people alert but not alarmed.

"I would urge the public to report any suspicious activity to the police and security services in their continuing efforts to discover, track and disrupt terrorist activity."

The director general of the Security Service, Jonathan Evans, said last week there had been a "persistent rise" in "activity and ambition" by dissident groups in Northern Ireland over the past three years.

While they did not have the capacity to return to the levels of violence caused by the Provisional IRA at the height of the Ulster Troubles, he said they still represented "a real and rising security challenge".

His warning came after the Real IRA publicly threatened to target banks and other financial institutions in the City of London, accusing them of "financing Britain's colonial and capitalist system".

In a speech to the Worshipful Company of Security Professionals in the City, Mr Evans said while MI5's "main effort" remained focused on international terrorism, it had been necessary to reinforce its presence in Northern Ireland to deal with the heightened threat.

He acknowledged the recent rise in activity by dissident republicans had not been foreseen, having been assumed just three years ago to be "low and likely to decline further".

Since the start of the year there had been more than 30 attacks or attempted attacks on national security targets by dissident republicans, compared with just over 20 for the whole of last year, he said.

Mr Evans added: "Perhaps we were giving insufficient weight to the pattern of history over the last hundred years, which shows that, whenever the main body of Irish republicanism has reached a political accommodation and rejoined constitutional politics, a hard-line rejectionist group would fragment off and continue with the so-called armed struggle."

Yesterday, a judge in Lithuania judge postponed a hearing in the trial of a suspected IRA dissident accused of trying to purchase weapons and explosives in the Baltic country.

Michael Campbell, the brother of a senior Real IRA figure in Ireland, was arrested in January 2008 in an international sting operation when he allegedly handed cash to an undercover Lithuanian agent posing as a weapons supplier.