Violent clashes broke out in central Dublin on Thursday evening, with vehicles torched and riot police attacked by a far-right mob following a knife attack at a school in the Irish city.

A five-year-old girl was seriously injured in the attack earlier in the day. A woman and two other young children were also hospitalised.

Superintendent Liam Geraghty said at a media briefing that preliminary indications are that a man attacked a number of people on Parnell Square East.

He said that police believe that it was “a standalone incident, not necessarily connected to any wider issues that are ongoing in the country or in the city, and we need to identify the exact reasons for that happening”.

Irish police said the girl was receiving emergency medical treatment in a Dublin hospital. Soon after that announcement, at least 100 people took to the streets, some armed with metal bars and covering their faces.

Police said more than 400 officers were deployed in Dublin city centre to contain the unrest. A police cordon was also set up around the Irish parliament building, Leinster House, and officers from the Mounted Support Unit were in nearby Grafton Street.

There were clashes with riot police as some demonstrators let off flares and fireworks, while others grabbed chairs and stools from outside bars and restaurants.

A number of police vehicles and a tram were damaged during the disorder, while a bus and car were also set on fire on the city’s O’Connell Bridge.

Police and politicians called for calm and warned against misinformation over the attack earlier in the day.

The police said far-right agitators had started the violence after a small group of anti-immigrant protesters arrived at the scene of the stabbing attack and clashed with police.