A second man has been shot dead in Dublin in an apparent gangland feud which is suspected to involve drugs gangs in Ireland and Spain.

The man in his 50s was gunned down on Poplar Row, North Strand in the north inner city just three days after David Byrne, 33, from Crumlin on the southside of the Irish capital, was murdered at a weigh-in for a boxing match in the Regency Hotel.

The latest victim was named locally as Eddie Hutch.

The first murder was claimed by a group purporting to be the Continuity IRA, a dissident republican splinter faction, but that drew scepticism from detectives immersed in gangland investigations.

In a statement the Garda press office said: "Gardai are aware of the recent statement to the media and are keeping an open mind in relation to the criminal groups involved as part of their investigations."

Justice Minister Frances Fitzgerald appealed for any other gang members who fear for their lives to come forward and seek protection.

"Tonight's fatal shooting in Dublin is another deplorable example of the ruthlessness of gangland criminals. It seems that some gangs are intent on waging a feud where human life counts for nothing," she said.

"The gardai will take all necessary steps to try to prevent further bloodshed but we have to recognise the challenges they face. Members of gangs who have fears for their safety should come forward to the gardai."

Garda Commissioner Noirin O'Sullivan and senior investigators will hold talks with the minister over the escalating feud on Tuesday.

The Regency Hotel attack was carried out by a six strong gang - three of whom were armed with Kalashnikov assault rifles and dressed in Swat team uniforms and helmets.

Another armed with a handgun was dressed as a woman and had an auburn wig and a fifth wore a flat cap and tracksuit.

About 300 people were in the hotel in the build-up to a title fight billed Clash Of The Clans when the Byrne murder was carried out.

The bout was promoted by Frank Warren and MGM Promotions based in Marbella.

In the immediate aftermath Byrne's murder was linked to a feud between major organised crime outfits in Dublin and the south of Spain with speculation that it was retaliation for the murder of 34-year-old Gary Hutch at the Angel de Miraflores apartment complex on the Costa del Sol in September last year.

There were also reports that Daniel Kinahan, who manages some boxers in the MGM camp, was in the Regency at the time of the attack.

He is the son of Christy Kinahan who was arrested in a mansion in Spain in 2010 as part of an investigation into an international drugs and money laundering racket. Kinahan senior has not been charged.

Senior gardai initially ruled out terrorist involvement for the Regency attack.

The first claim of responsibility - attributed to dissident republicans and made with a code word to the BBC in Belfast - drew scepticism from seasoned commentators in Dublin while the top brass in the Garda said they were keeping an open mind and pointed to a "criminal" element.

In a second statement, issued to the Irish Daily Mirror hours later and again purportedly from the Continuity IRA, dissident republicans dismissed the first claim as bogus.

"The Continuity IRA wish to make it clear that we did not have any involvement in Friday's shooting at the Regency Hotel," it said.

"We have absolutely no involvement in criminal feuds. We see the false claim that the CIRA were involved in this act as another attempt to tarnish the name of the organisation."

Des Dalton, president of Republican Sinn Fein, said he had spoken to republican sources who had confirmed the second statement and rejected the claim of responsibility.

"I have been told that it was a bogus statement and an attempt to smear the Continuity IRA," he said.

The latest victim was murdered at a flat complex in a disadvantaged area of north Dublin.

He is understood to be the brother of Gerry Hutch, nicknamed The Monk, and an uncle of murdered Gary Hutch, believed to be the first victim in the bloody feud when he was gunned down almost five months ago.

It is believed a gang of at least four men were involved in the latest killing.

Sinn Fein leader Gerry Adams urged community support to catch those responsible for the killings.

"Those behind this latest shooting, and those behind the dreadful attack last Friday at the Regency Hotel, must be apprehended and taken off our streets," he said.