Disorder broke out in Dublin on Thursday night after a woman and three young children were injured in a knife attack near a school in the Irish capital.
Buses and trams were torched and a shop was looted during riots in the city centre.
Demonstrators let off flares and fireworks and clashed with riot police. A police cordon was set up around the Irish Parliament building, Leinster House, and officers from the Garda Mounted Support Unit were in nearby Grafton Street.
In a video statement on social media, Ch Supt Patrick McMenamin said some members of the police force had been attacked and assaulted. But he added that there were no serious injuries, and that "Dublin city centre is now calm and returning to normal".
The Irish justice minister, Helen McEntee, described the scenes as “intolerable” and said a "thuggish and manipulative element must not be allowed to use an appalling tragedy to wreak havoc".
Police detained a man in his 50s who stabbed the woman and three young children. They said they were not seeking other suspects.
Earlier on Thursday, Garda Superintendent Liam Geraghty said officers were keeping an open mind in terms of the investigation but were "satisfied there is no terrorist link".
However, at an evening press conference, Mr Harris was asked about a potential terrorist link and said: "I have never ruled out any possible motive for this attack... all lines of inquiry are open to determine the motive for this attack.
"Until we’re sure what the motive is then we have to keep an open mind as to why this happened."
Why are there riots in Dublin?
Ireland’s police chief Drew Harris blamed a "complete lunatic faction driven by far-right ideology" for the disorder, warning against the spread of "misinformation".
Is it safe to travel to Dublin?
On the Government's foreign travel website, the Ireland entry says: "On 23 November 2023, following a knife attack, there have been reports of protests and unrest around Parnell Street East and O’Connell Street in central Dublin.
"You should avoid these areas and follow advice of local authorities."
