People should give information about the death of a man stabbed after a pub fight, Sinn Fein's Gerry Adams says.
Robert McCartney, 33, was murdered in Belfast city centre
Robert McCartney, 33, was murdered in Belfast two weeks ago, and his sister has said she believed republicans were pressuring witnesses not to talk.
Mr Adams said he supported their search for justice: "No one has any right, as has been claimed, to prevent anyone from helping the McCartney family."
He said those who would not talk to the police should contact the family.
"People with reservations about assisting the PSNI should give any information they might have either to the family, a solicitor or any other authoritative or reputable person or body," he said.
He added: "I want to make it absolutely clear that no one involved acted as a republican or on behalf of republicans."
Detectives do not believe the IRA sanctioned the murder but the victim's sister, Paula, believes republicans have been putting pressure on witnesses not to talk.
"Their cover-up and their clean-up operation afterwards was meticulous," she said.
"It's just getting more evidence and getting more people to come forward and be brave and hand these people over.
"They're no good to man nor beast - they're just psychopaths with power," said Ms McCartney on BBC's Radio Ulster Talkback programme on Monday.
Several people questioned in relation to the 33-year-old's death were released without charge.
SDLP leader Mark Durkan has said he will share his concerns over the murder of Mr McCartney with US Special Envoy Mitchell Reiss in Washington.
Mr Durkan met Mr McCartney's family on Sunday.
He said the "full force of the IRA has been used to intimidate witnesses and prevent the killers from being brought to justice".
Paula McCartney says republicans are pressuring witnesses
Mr Durkan said: "There is power being used to prevent this brutal, brutal crime being properly investigated.
"The family are very clear - they want proper justice by due process."
Mr Durkan said he would be briefing Mr Reiss this week "on this appalling murder and the organised cover-up and intimidation that is occurring".
The police said almost 500 lines of inquiry were being followed by detectives investigating the murder.
They also said a large quantity of CCTV pictures were being examined.
However, detectives refused to comment on claims that a tape was missing from the bar where the fight took place.
The murder weapon has not yet been found.