Three young children are among five people injured following a “serious public order incident”outside a school in Dublin city centre.
Police said the three children, a man and a woman were taken to hospitals around Dublin shortly after 1.30pm.
One of the children, a girl, and the woman are being treated for serious injuries.
The other two children and the man are being treated for less serious injuries, according to police.
Irish Prime Minister Leo Varadkar said a suspect has been detained. Earlier, police said they are not looking for anyone else at this time.
The scene at Parnell Square East remains sealed off and police were being assisted by other emergency services.
Stephen Murphy, Sky News’ Ireland correspondent, said witnesses have told police they saw a man, who was reportedly wielding a knife, “attack several young people” as they left school.
The school is believed to be an Irish-speaking primary school.
“It appears that bystanders and eyewitnesses have played a huge role in bringing this incident to a halt,” Murphy said.
“Witnesses have spoken of seeing several bystanders become involved to try and intervene and restrain this man.”
He described Parnell Square as an extremely busy area “right in the heart of Dublin city”.
“Five casualties have been taken to various hospitals in the Dublin region,” an Irish police spokesperson said.
“An Garda Siochana is in contact with parents of all three injured children.”
Helen McEntee, Irish justice minister, said she was “deeply shocked” by the “appalling attack on three innocent children and a woman”.
“All our thoughts are with those injured, especially with the children, their parents and families, during this extremely difficult period,” she said.