LONDON (AP) — Britain raised the terror threat level Friday posed by Irish Republican Army dissidents, who have mounted repeated attacks in Northern Ireland and recently threatened to start targeting London bankers.

The level has changed from "moderate" to "substantial," the middle rung on the five-point threat scale. This means the threat has risen to a point where an attack is considered a strong possibility.

The existing threat from al-Qaida-inspired groups in Britain has long been rated at the higher level of "severe." The currently unused top threat level of "critical" would mean British anti-terrorist officials consider an attack to be imminent.

The heightened threat posed by IRA die-hards comes just weeks before the start of the annual conference of the governing Conservative Party, long a prized IRA target. In 1984, the outlawed organization nearly killed then-Prime Minister Margaret Thatcher with a bomb that devastated the Conservatives' conference hotel, killing five and wounding 30.

Friday's announcement represented the first time that Britain's Home Office, responsible for law and order in England and Wales, made public its threat assessment of Irish terrorism.

"When we set these levels of threat, we're taking into account any information available to us. Often it is just a precaution, but people have to take these threats very seriously," Foreign Secretary William Hague said in an interview with The Associated Press at U.N. headquarters in New York.

Home Secretary Theresa May said announcing the threat level change was "in the interests of transparency and to encourage people to remain vigilant."

"We're putting more resources on this because of the increased activity," a British government official said on condition of anonymity because of the sensitivity of his work. "There is certainly the perception that the threat has escalated."

IRA splinter groups continue to pursue violence in hopes of upsetting Northern Ireland's Catholic-Protestant government and other achievements of the 1998 peace accord in the British territory. Police say the dissidents actively seek to recruit veterans of the mainstream IRA, which formally renounced violence and disarmed in 2005.

"It is a worrying sign that the intelligence services have upgraded the threat level, which underlines the need for adequate police resources to tackle this threat and stamp it out completely," said First Minister Peter Robinson, the Protestant leader of the Belfast coalition.

Dissidents committed the deadliest attack of the entire four-decade Northern Ireland conflict, a 1998 car-bomb strike on the town of Omagh that killed 29 people, mostly women and children. Their efforts to bomb targets in England ended in 2001 when anti-terrorist officers tracked down and arrested the dissidents' only unit based in England.

However, ever since the Catholic-Protestant government's formation in 2007, the dissidents have been trying to undermine the coalition with renewed violence. In March 2009, they fatally shot two off-duty British soldiers and a policeman sitting in his car — the first such killings of Northern Ireland security forces since 1998.

But about 30 dissident IRA attacks this year — including five car bombs detonated outside police bases, a courthouse and the regional headquarters of the British MI5 spying agency — have caused only minor damage and injured nobody seriously.

Last week, the MI5 director, Jonathan Evans, warned in a speech that IRA dissidents could mount attacks in England for the first time since August 2001, when a car bomb damaged a shopping center in London's western suburbs and injured 11 people.

Earlier this month, The Guardian newspaper quoted the dissident Real IRA group as saying it planned attacks in England and wanted to assassinate top London bankers.


Associated Press Writer Shawn Pogatchnik in Dublin contributed to this report.