Six people are in hospital following a large scale “violent disturbance” in Cardiff city centre.
Police and ambulance crews were called to an area of Queen Street at about 21:50 GMT on Saturday.
One of those in hospital suffered head injuries and is in a serious condition and three others are thought to have been stabbed, South Wales Police said.
Two people have been arrested on suspicion of violent disorder and are in custody in Cardiff Bay.
The injured are all being treated at the University Hospital of Wales, police said.
Officers were alerted by “multiple reports” of a “large disturbance” on Queen Street and an investigation is under way.
Witnesses to the incident, or what happened before or after the violence, are urged to call police via 101.