Ireland's prime minister says he's "absolutely appalled" by an assault in the country's capital that resulted in the death of a tourist from Montreal.

Simon Harris on Wednesday described Neno Dolmajian's death in Dublin as "reprehensible" and "horrific" and told parliament the death is now being investigated as a murder.

"I'm absolutely appalled at the recent vicious attack in Dublin city centre which resulted in the death of a young man, Neno Dolmajian, and my thoughts are with his loved ones," he said.

"A man who came from Montreal to, as you say, enjoy the best of our city, the best of our country, who came here on his holidays."

Ireland's national police confirmed Tuesday that a man in his 40s had died in hospital after an assault that occurred on O'Connell and Cathal Brugha streets in the early hours of June 23.

Police provided little detail, but said in an initial news release that officers on patrol were alerted to two incidents involving "a number of individuals" at around 1 a.m. and arrested one man in his 20s and another in his 30s. 

The victim was taken to hospital in serious condition, where he died more than a week later.

Police said Tuesday that four men have now been arrested in connection with the incident, and two of them have been charged.

Police did not identify the victim, who has been named by politicians and media outlets and described as a 41-year-old Canadian tourist.

Opposition Leader Mary Lou McDonald said Dolmajian died in hospital "with his parents and sister at his bedside" after being severely beaten. 

She challenged Harris to do more about the anti-social behaviour, drug dealing and gang activity she said were creating "a daily atmosphere of fear and intimidation" in Dublin's city centre.

"The vicious attack that led to Mr. Dolmajian's death again highlights the hard reality that our city centre is not safe, and I say this as a very proud Dubliner," she said.

Global Affairs Canada said only that it was "aware of the death of a Canadian citizen in Ireland," and was providing consular assistance to the family.