The family of a Catholic man slain by IRA members demanded an end on Wednesday to the intimidation that dissuades Catholics from cooperating with police a crucial but often overlooked problem in the peace process.

Forklift operator Robert McCartney, 33, was fatally stabbed outside a downtown Belfast pub on January 30 when he tried to defend his friend, Brendan Devine, from what witnesses described as a knife-wielding Irish Republican Army gang. Devine survived despite having his throat and abdomen slashed.

What happened next illustrated the power the IRA wields in its Catholic power bases a hold that McCartney's five sisters say must be broken.

"His attackers went back into the pub and locked the doors. They ordered everyone not to make phone calls, even for an ambulance," said Paula McCartney, who has spoken to many of the more than 50 witnesses _ all of whom are too afraid of a possible IRA death sentence to make a statement to detectives.

Police arrested seven men, including a former commander of the Belfast IRA who lives near McCartney's home in a hard-line Catholic enclave called Short Strand.

Detectives say none of the suspects talked, and all walked free. They said IRA members quickly washed their clothes after the killing and destroyed other forensic evidence. They re-arrested one of the suspects for further questioning on Wednesday night.

Earlier, three of McCartney's sisters met the American consul-general in Belfast, Dean Pittman, as part of their efforts to mobilise pressure on Sinn Fein, the IRA-linked party.

The IRA's seven-man command denied official involvement on Wednesday night. Its statement left open the possibility that IRA members acting individually killed McCartney.

"Those who were involved must take responsibility for their own actions, which run contrary to republican ideals," the IRA said.

That statement and several others this week by Sinn Fein leaders have pointedly refused to encourage witnesses to contact detectives a crime of "informing" that, in IRA eyes, merits execution.

Instead, Sinn Fein leader Gerry Adams advised witnesses to pass on information to other "authoritative or reputable" people, such as lawyers or Catholic priests.

But McCartney's family, several of whom identify themselves as past Sinn Fein supporters, rejected the IRA statement as misleading and called Adams' appeal too weak.

They said they already accepted that the IRA men killed McCartney.