Armed police were sent to a Cardiff suburb after reports that a woman had been assaulted.
A 30-year-old woman was treated by paramedics and has been taken to hospital, after the incident in the Llanishen area.
A 32-year-old man was arrested in Trenchard Drive, Llanishen, just after 1pm.
Police officers were reported to have been seen at nearby Llanishen High School.
A spokeswoman for South Wales Police said: “Armed police were deployed as a precaution to ensure the safety of the public and officers while arrest enquiries were conducted in the area.”
A Welsh Ambulance Service spokesperson said: “We were called at 12.18pm to reports of a female who had been assaulted on Kimberley Terrace, Llanishen.
“We sent a community first responder, a rapid response vehicle and an emergency ambulance to the scene and a female was taken to the University Hospital of Wales.”
No-one else was injured during this incident.
The spokeswoman added that the arrested man remains in police custody and an investigation is on-going.