The IRA has denied involvement in the murder of Mr Robert McCartney. A statement last night, signed by P. O'Neill, said the IRA wished "to make it absolutely clear that no one should hinder or impede the McCartney family in their search for truth and justice", writes Dan Keenan, Northern News Editor.
His murder last month was "contrary to republican ideals", the statement said.
Separately, the Sinn Féin president, Mr Gerry Adams, said he could be wrong about IRA involvement in the Northern Bank robbery.
Speaking on radio during a visit to Madrid, he said "No one knows who robbed the Northern Bank.
"An opinion has been given that the IRA was involved. The IRA has said it was not and I believe them.
"Now, maybe I'm wrong. What I can say categorically is that Sinn Féin was not involved."
Soon after the remarks were broadcast in Northern Ireland, Mr Adams released a statement saying: "Remarks I made in Madrid in respect of the Northern Bank robbery have been misrepresented.
"I made it clear that the IRA has said it was not involved and that I believed its disclaimer.
"Any other interpretation of my remarks is malicious and misleading."
The IRA's statement on Mr McCartney's murder in Belfast is the second from P. O'Neill this month and the fourth this year.
Two weeks ago a statement in O'Neill's name announced the IRA was withdrawing its earlier decommissioning proposals, while in January, a P. O'Neill statement denied the IRA was involved in the Northern Bank robbery.
The IRA's New Year statement on January 6th was also signed P. O'Neill.
Yesterday's statement came just before the PSNI made another arrest in relation to Mr McCartney's death. Mr McCartney was beaten and stabbed after a bar fight witnessed by more than 100 people.
The IRA statement followed an appeal by Mr McCartney's sisters for an end to alleged IRA intimidation of witnesses.
They questioned Sinn Féin's stance on the police investigation. "The call for those with information to go to a solicitor, priest or ourselves raises questions such as, what would this achieve?
"Would this bring Robert's murderers to justice?" the family asked after a meeting with the US consul in Belfast. Sinn Féin's Mr Gerry Kelly said the party was doing "all it can" and accused opponents of using Mr McCartney's murder and his party's response to "bash Sinn Féin".
Speaking in Washington, the SDLP leader, Mr Mark Durkan, said there would not have been an IRA statement were it not for the "valiant" efforts of the McCartney sisters.