BELFAST, Northern Ireland (AP) _ Northern Ireland's major party today demanded the expulsion of the IRA-allied Sinn Fein party from peace talks because of killings this week blamed on the Irish Republican Army.

Ulster Unionist leader David Trimble said he expects the negotiations on Northern Ireland's future to concentrate on whether to expel Sinn Fein ``because of the murders being committed by the IRA _ and the very clear breach by the IRA of its cease-fire.''

The talks, which continued today in Belfast, are inching toward the creation of a new Northern Ireland lawmaking assembly in which Protestants and Catholics would govern in coalition. Alone among the participating parties, Sinn Fein flatly opposes the plan because it wants to abolish Northern Ireland, not reform it.

No group has claimed responsibility for the separate shooting deaths of Protestant militant Bobby Dougan and Belfast drug dealer Brendan Campbell.

Police today arrested four more men in Catholic west Belfast to be interrogated about Dougan's death. Detectives earlier characterized three men arrested Tuesday in the killing as IRA suspects.

Dougan's killing put pressure on the north's major pro-British Protestant gang, the Ulster Defense Association, to retaliate against Catholics. Dougan was a UDA member whom the IRA shot in the stomach in 1994.

Initial suspicions that the Irish National Liberation Army killed Dougan were dispelled when the anti-British gang, which opposes the 6-month-old IRA truce, emphatically denied involvement.

The IRA was immediately suspected of slaying Campbell, whose bullet-proof vest had saved his life in another gun attack last month attributed to the IRA. In 1995 and 1996, during a previous cease-fire, the IRA killed eight suspected drug dealers.

Under rules required by the peace talks' chairman, former U.S. Sen. George Mitchell, all participants formally pledged a six-point renunciation of violence. That committed each party _ particularly those linked with paramilitary groups _ to ``actively oppose'' any resumption of violence or face expulsion.

In an implicit reference to Sinn Fein, the British government's No. 2 minister in Northern Ireland, Paul Murphy, warned Tuesday of ``serious implications'' if either slaying ``is shown to have been committed by an organization connected with a participant in these talks.''

Two weeks ago, the British and Irish governments expelled the UDA's Ulster Democratic Party from the negotiations after Northern Ireland's police chief, Ronnie Flanagan, said the UDA had killed three Catholics in violation of its 1994 cease-fire.

The UDA then admitted it had killed some Catholics as a ``measured military response'' to the Irish National Liberation Army's killing of a UDA member Jan. 19.

Trimble said the governments' expulsion of the Ulster Democrats set ``a very clear precedent'' for expelling Sinn Fein.

Any more killings attributed to the UDA would ensure the continued exclusion of the Ulster Democrats from the talks, which are supposed to conclude in May.

The IRA declared a cease-fire in July 1997 to permit Sinn Fein to join the negotiations.

At talks today, Trimble's Ulster Unionists unveiled a document outlining their vision of a peace settlement. It played down the importance of building a new cross-border council in which lawmakers from Northern Ireland and the Irish Republic would cooperate in areas of common interest.

Forming a powerful cross-border council is considered critical for Catholic politicians, who want to see the north united with the rest of Ireland.