All-out gang war has broken out in Dublin, with two high-profile murders within three days.

There are real fears there will be more shootings in the feud between two rival gangs.

On Monday night Eddie Hutch, 59, brother of former gangland boss Gerry “The Monk” Hutch, was shot dead by four masked men at his home in Poplar Row in Dublin’s north inner city.

Detectives have no doubt it was a revenge killing for the murder three days earlier of leading Dublin criminal David Byrne, 33, in a prohibition era, Chicago-style attack at the Regency Hotel, also on Dublin’s North Side.

Byrne’s murder at a boxing weigh-in before 200 people, including children, was believed to have been in retaliation for last September's assassination of 34-year-old Gary Hutch, a nephew of both Eddie and The Monk, near Marbella in southern Spain.

Gary Hutch is believed to have been shot dead by members of a gang run by Spain-based Dublin criminal Christy “Dapper Don” Kinahan, 59, with whom Byrne worked in massive ongoing operations to smuggle drugs into Britain and Ireland. Gary Hutch was believed by the Kinahan gang to have been a police informer.

Kinahan, who has served terms in prison, lives in a $7 million mansion near Marbella. Kinihan is thought to have stashed away hundreds of millions of euros from his criminal activities.

His son, Daniel, a boxing promoter, was believed to have been a target in the Friday Regency Hotel shooting by a gang of six, including three men disguised as an elite Swat unit from the gardai (Irish police), a man dressed as a woman, and two others.

Daniel Kinahan, who traveled from Spain for the boxing tournament – abandoned after the shootout – was reported to have escaped by diving with his bodyguard through a window.

Two of murder victim David Byrne’s criminal associates were also injured in the shooting and received hospital treatment. The hotel attack gang used IRA-style AK47 rifles and pistols in the attack.

Although the Continuity IRA on Monday claimed responsibility for the attack in a coded phone call to the BBC – claiming it was in revenge for the 2012 murder of Real IRA Dublin boss Alan Ryan – Gardai were skeptical the call was genuine. They are convinced it is a gangland war not involving paramilitaries.

Within hours of the call, and despite a huge Garda presence at checkpoints throughout Dublin, four men drove a silver BMW to Eddie Hutch’s home where they killed him immediately with several shots.

They abandoned their car a short distance away and made efforts to set fire to it, but it was seized in time by Gardai who also found balaclavas and a can of petrol inside the vehicle.

In the Friday shooting at the Regency Hotel – a familiar sight to tourists on the way to Dublin Airport – one child was heard on a video phone-recording scream, “Daddy, help me! What was that?”

Kevin McAnena, a sports reporter for BBC Radio Foyle in Northern Ireland who was at the weigh-in, said he dived behind a desk and a gunman peered over and aimed a rifle at him but didn’t fire.

McAnena added, “I was looking down the barrel of the gun and thought I was going to die. It was utterly terrifying.”

Detectives believe some of the gang may have been imported from abroad, but eyewitnesses also said at least one of the masked gunmen disguised as a Garda spoke with a Dublin accent.

Gardai collected video footage and photographs from the scene and they believe they are close to identifying some of the gunmen. They also say evidence in the car seized after the Eddie Hutch murder will help them trace the gunmen who killed him.

Eddie Hutch was known to the Gardai, but for mostly minor crimes. Although relatives were linked to gangland, he was not regarded as violent and was not believed to be criminally active.