A TERROR attack in Britain by dissident republicans is now again a “strong possibility” prompting the government to lift the terror alert, as violence again flares from the troubled region.

Britain’s intelligence service MI5 has increased the level of threat posed by Northern Ireland-related terrorism from moderate to substantial, the third most serious category out of five.

Home Secretary Theresa May said the move “reflects the continuing threat from dissident republican activity”.

The threat level in Northern Ireland remains unchanged at “severe” which means an attack is “highly likely”.

There has been growing dissident republican violence in recent months in Northern Ireland, predominantly Belfast and in particular since the March murder of prison officer Adrian Ismay by a group calling themselves the “New IRA”.

A deliveryman was also recently killed after being lured to his death by suspected dissidents who had placed a bogus order for Chinese food with his outlet he runs with his wife.

The couple was suspicious because the order was made from a phonebox in north Belfast but they accepted the “chicken curry” order anyway. On the same night two others were shot, including a 17-year-old boy in the legs in what police suspect are “punishment attacks”.

At least 25 people are facing paramilitary-style attacks in north Belfast from dissidents trying to control the area. The dissidents, who derive most of their funds through criminality, such as fuel laundering and cigarette smuggling, command little community support but retain a tight grip in certain areas through fear and punishment attacks.

Police in Northern Ireland have cautioned that their capabilities, in isolated incidents, could be increasing as they acquire more sophisticated weaponry like mortar bombs and high calibre assault rifles.

Dissidents have also claimed to have up to a tonne of “newly acquired” Semtex — the odourless plastic explosive which was used widely by the Provisional IRA during the 1980s.

“The main focus of violent dissident republican activity continues to be in Northern Ireland, where they have targeted the brave police and prison officers who serve their communities day in and day out,” Ms May said yesterday.

She added: “However it is sensible, given their stated aims, that the public in Great Britain should also remain vigilant and report any suspicious activity to the police. But we should not be alarmed, and this should not affect how we go about our daily lives.”

The raising of the terror alert for IRA-style attack in Britain was the first for five years.

Democratic Unionist MP Jeffrey Donaldson expressed surprise at this latest security assessment and was seeking an urgent Privy Council briefing on the matter although he recognised the need.

“It is evident that dissident republicans are now active in Great Britain and are examining potential targets. Obviously that’s a matter of concern.”

“We had no prior indication that the threat level had been increasing. In Northern Ireland, the threat has been severe for some time but quite clearly this is a new development in terms of dissident republican activity.”