A witness to the serious incident in Dublin city centre has detailed attempts to disarm the man involved in the suspected stabbing, calling it "absolutely bedlam".

A five-year-old girl and a woman who worked in a crèche were seriously injured in the incident, where three other people, including two other children, have been injured.

All five injured people have been taken to different hospitals across Dublin, including Children's Health Ireland at Crumlin and the Mater Hospital.

Siobhan Kearney, whose brother Liam Dunne died in the fire at the Stardust nightclub in 1981, was attending the inquests into that tragedy at the nearby Rotunda Hospital when the stabbing happened.

She said she saw it unfold from across the road and when asked whether the children and woman were victims of a stabbing, she said that she was told they were.

"Without thinking, I just took across the road to help out. We got another young man, disarmed him [the attacker] with the knife, another man took the knife and put it away for the garda to find it," Ms Kearney said.

"Two children and the woman were taken back into the school where they were coming from. It was absolutely bedlam."

She said that the children were about six years of age, and that she had thought the woman was a teacher or bystander.

On the man with the knife, she said that he was on the ground and there were a lot of people trying to restrain him.

"Me and an American lady formed a ring around him saying we'd wait on the garda."

She said that the ambulance came first within three or four minutes and all the emergency services were there in five minutes.