A man has been arrested on suspicion of murder after the death of a 21-year-old woman who was found unconscious with serious injuries.
Police said officers were called to Springwell Road in the Holbeck area of Leeds early on Wednesday and found the victim, thought to have been a sex worker, with "injuries consistent with an assault".
She was taken to Leeds General Infirmary but was pronounced dead a short time later.
Detective Superintendent Simon Atkinson, of West Yorkshire Police Homicide and Major Enquiry Team, said: "Clearly a young woman has lost her life in violent circumstances and it is absolutely vital that anyone who saw anything suspicious during the evening and into the early hours contacts us immediately."
He confirmed that a 38-year-old man had been arrested.
Mr Atkinson said: "We are treating this woman's death as murder and a full investigation has been launched. Our inquiries are currently at a very early stage and we would like to hear from anyone who was in the area of Springwell Road between 8pm last night and about 1.30am this morning."
Chief Superintendent Paul Money, Leeds District Commander, said: "We are acutely aware that the murder of this young woman will cause understandable concern in the community and we are keen to reassure people that we are doing everything we can to support and assist the investigation to trace the person responsible.
"Officers will be focusing increased patrols into the area for the foreseeable future to provide a visible reassurance to people."