A man out jogging in Fartown was attacked and stabbed in the neck in broad daylight, witnesses say.
The man was reportedly jogging just after noon in Red Doles Road, Fartown, when he was stabbed in the neck and chest.
He was taken to hospital in an ambulance although an air ambulance had been called.
Detectives are currently probing the scene for evidence.
One person said the victim was targeted in the chest and neck.
Another resident said her young children alerted her to the drama.
She said: "My children didn't see it but they are very upset by the amount of blood. I'm having a hard time explaining it to them. "
West Yorkshire Police said: "Police were called to Red Doles Road at 12.09pm to a report of a serious assault.
"A man has been taken to hospital with serious injuries.
"Enquiries remain ongoing at the scene."