Armed police launched a manhunt after residents were urged to lock their doors and windows following a man being seriously assaulted.
South Wales Police said the man was taken to hospital and remains in a critical condition after the incident at around 5.30pm in Clydach, Swansea.
There is a significant police presence in the area as the search for the suspect, who is known to the victim, continues, Wales Online reports.
Residents near Gellionen Road have been told to lock their windows and doors, according to those in the area.
Pictures appear to show an ambulance and armed police in the area.
Police have been telling those in the area "not to worry", according to one nearby resident.
They added that ambulance, rural crime scene and armed police remain in the area.
The resident said the police wouldn't say "what the man looks like".
Another resident said a large police presence has been in place in the area near the area since around 5.30pm.
The resident, who did not want to be named, said: "We were told a man was running around with a knife.
"The helicopter is out again for the third time. The police told us to lock all windows and doors. This is so scary."
Swansea Police tweeted: "There is a significant police presence in the area as a search for the suspect who is known to the victim continues.”
The Welsh Ambulance Service has confirmed they were called to the incident following a request from police.
Two ambulances and a hazardous area response team were among those to respond to the incident.
One person was taken to Morriston Hospital, a spokesman said.