A man in his 50s has been stabbed confronting an intruder in his garden in Dundonald, on the outskirts of east Belfast, on Wednesday morning.
The victim suffered a head injury and wounds to his abdomen in the incident, which happened shortly before 9.30am.
He is being treated in hospital and investigating police say his condition is not yet known.
PSNI Detective Inspector Wallace said: “We would like to hear from anyone who may have seen a man aged in his 20s acting suspiciously in the Grangewood Road, Dunlady Road or Ballyregan Road area between 9am and 9.30am today.
“Anyone with information - or CCTV covering their house which could have captured images during the time period we are most interested in - should contact police on 101.”