Violent protests have erupted in Ireland’s capital, Dublin, after four people including three young children were injured in a suspected knife attack, writes Al Jazeera.

Crowds of protesters clashed with police in the city centre on Thursday hours after a five-year-old girl and a woman in her 30s were seriously injured in the attack outside a school in Dublin. Police said they were receiving emergency treatment.

Two other children, a 5-year-old boy and a 6-year-old girl, suffered less serious injuries. The boy has been discharged from hospital. According to Irish broadcaster RTE, the woman works at the school and cares for the children.

A man in his 50s was detained in relation to the incident, and was also hospitalised with serious injuries. Police said in a statement they were “following a definite line of inquiry” and were “not looking for any other person at this time”.

“I’m very strongly satisfied from our inquiries that there is no terror-related activity”, Superintendent Liam Geraghty told reporters after the attack, adding: “It would appear to be a standalone attack”.

Ireland’s police chief Drew Harris later told the media that “all lines of inquiry” were open to determine the motive. “I never ruled out any possible motive for this attack”, Harris said.