The report by Northern Ireland's Police Ombudsman into the murders of six Catholic men in a bar at Loughinisland, Co. Down on 18 June 1994 is "deeply disturbing", Ireland's Minister for Foreign Affairs, Charlie Flanagan has said.

The Police Ombudsman Dr Michael Maguire, who investigated the killings, made a dramatic statement that in his opinion "I have no hesitation in unambiguously determining that collusion is a significant feature of the Loughinisland murders."

He was referring to elements of the RUC police force colluding in the murders with the killers.

The attack on the Heights Bar was carried out by members of the Loyalist paramilitary group, the Ulster Volunteer Force (UVF). The victims were watching Ireland's dramatic win over Italy in an opening round of the World Cup soccer tournament at Giants Stadium in New Jersey.

What should have been a joyous occasion turned into a major tragedy for Adrian Rogan (34), Patrick O’Hare (35), Eamon Byrne (39), Malcolm Jenkinson (53), Daniel McCreanor (59) and 87-year-old Barney Green as well the five persons who were injured, as well as the grieving families of the victims.

No one has ever been prosecuted for the killings. In his 160-page report, Police Ombudsman Dr. Michael Maguire noted that it had been "a central complaint of the families that there was ‘collusion’ between elements within the police and loyalist paramilitaries".

Read more: A survivor’s tale: The 1994 Loughinisland massacre

He found that the nature of the relationship between the police and their informants within loyalist paramilitary organizations had "undermined the investigative process" .

He added: "There were many examples of failures to pass on intelligence to investigators. This meant that investigative lines of inquiry were not followed and individuals, who might have been subject to detailed and robust investigation, were effectively excluded from consideration."

Dr. Maguire said there was a "hear no evil, see no evil, speak no evil" approach to the use of informants, which potentially frustrated the police investigation into the attack.

He added: "It is of particular concern that Special Branch continued to engage in a relationship with sources they identified in intelligence reporting as likely to have been involved at some level in the Loughinisland atrocity."

It is believed that the attack was intended as a response to the killings of senior UVF figures on Belfast's Shankill Road two days earlier. The Ombudsman said he had not been able to determine with any certainty why the Heights Bar was chosen but he added that the attack "was sectarian as the targets were members of the Catholic community."

He said that the VZ58 rifle used in the Loughinisland attack was part of a shipment of arms brought into Northern Ireland by loyalist paramilitaries in late 1987/early 1988.

Responding to the report, Foreign Minister Flanagan said in a statement: "The Ombudsman’s findings are deeply disturbing – in particular his determination that 'collusion is a significant feature of the Loughinisland murders.

“The findings must now be carefully examined with a view to the question of further investigations and possible prosecutions," he added.

Daughter of Loughinisland victim says she 'feels vindicated':

— UTV (@utv) June 9, 2016

Opposition leader Mícheál Martin of Fianna Fáil said the victims were simply watching Ireland playing Italy in the World Cup soccer competition when they were ruthlessly gunned down by loyalist killers.

"The fact that the police, who were entrusted with protecting the community, were embroiled in collusion with the death squad responsible for the massacre is sinister and disturbing," the Fianna Fáil leader said.

He called on the British Secretary of State for Northern Ireland, Theresa Villiers to apologize for and retract a statement she made in a speech last February, where she said it wasn't the police or the British Army who "pulled the triggers at Loughinisland."

Villiers had said that "a pernicious counter-narrative" of the Troubles was emerging whereby responsibility for acts of terrorism was being shifted onto the security forces "through allegations of collusion, misuse of agents and informers or other forms of unlawful activity".

While the police and the army would always be judged by "the highest standards of integrity and professionalism", Ms Villiers added that "It wasn’t the RUC or the Army who planted the bombs at La Mon, Enniskillen, or the Shankill, or pulled the triggers at Loughinisland or Greysteel."

Martin said her comments were "misleading and hurtful given the details of serious collusion that have now emerged".

Sinn Féin President Gerry Adams said the Ombudsman's report was “just the latest exposing the depth of collusion involving British state forces and unionist paramilitaries".

Calling on the Fine Gael-led government in Dublin to take a stronger line on such issues, he said: “A step change in the Irish government’s response to collusion is urgently needed. It needs to put in place a consistent strategic engagement with the British government."

Sinn Féin TD Seán Crowe said the Loughinisland victims were subjected to "an unprovoked and sectarian attack that left six dead and five injured" and their families had waited 22 years for the report on the atrocity.

“The report is unambiguous. It shows clear and systemic collusion between British agents, the RUC and the UVF death squad who carried out the attack," he said.

Paddy McCreanor, nephew of victim Daniel McCreanor, said: "Collusion is no illusion and collusion happened. The truth has come out and that's all we ever wanted."

The families' lawyer Niall Murphy said: "This report is one of the most damning expositions of state collusion in mass murder that has ever been published."

'Collusion is no illusion,' say families of victims of Loughinisland murders

— Irish Examiner (@irishexaminer) June 9, 2016