The small breakaway Loyalist Volunteer Force and the republican Continuity Army Council, which opposes Sinn Fein's peace strategy, were banned from midnight last night.
The LVF is believed to be behind a number of recent attacks, including bombings across the border, while the Continuity Army Council has attempted a number of bombings since breaking away from the Provisional IRA because of opposition to their 1994 ceasefire.
The move, heralded earlier in the day by the Secretary of State for Northern Ireland, Mo Mowlam, came after multi-party talks resumed yesterday in Northern Ireland, overshadowed by uncertainties over the state of play within the IRA and Sinn Fein, fears of a violent marching season and low expectations of breakthroughs.
The funeral of a Royal Ulster Constabulary officer kicked to death by drunken loyalists cast a further pall over proceedings. Ms Mowlam warned that "a period of deep potential instability" lay ahead, with an obvious increase in "sectarian bigotry".
Ms Mowlam sought to inject impetus into the talks process by indicating that she wanted the parties to move on to substantive discussions within weeks.
This is seen as ambitious, given that the talks will shortly reach their first anniversary, following a year of arguments which has not even managed to produce an agreed agenda.
Meeting Ms Mowlam's target will therefore require a sharp burst of acceleration. This looks unlikely, given that the Rev Ian Paisley's Democratic Unionists are staying away from the talks until the Northern Ireland Forum, an adjunct of the talks proper, meets on Friday.
The parties have yet to agree on how to deal with arms decommissioning, which dominated proceedings for much of the past year.
As the parties gathered at Stormont, in east Belfast, a Sinn Fein delegation headed by the party president, Gerry Adams, arrived at the gates to enact the familiar ritual in which the republicans are denied entry because of the absence of an IRA ceasefire. This time they arrived to find the gates padlocked. The delegation handed in letters to the British and Irish governments, addressed the media, and left. Dublin's representative in the talks, Dick Spring, the foreign minister, replied that if the IRA declared a new ceasefire the governments could move very quickly in response.Reuse content