A man has been arrested on suspicion of murder after the death of a 21-year-old woman found unconscious with serious injuries.
Police said officers were called to Springwell Road, in the Holbeck area of Leeds, early on Wednesday and found sex worker Daria Pionko with "injuries consistent with an assault".
Miss Pionko - a Polish national living in Leeds - was was taken to Leeds General Infirmary but was pronounced dead a short time later, according to West Yorkshire Police.
Detective Superintendent Simon Atkinson confirmed that a 38-year-old man had been arrested and was in custody.
Mr Atkinson 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 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."
The detective was speaking at the scene of the attack, which is a trading estate about half a mile south of Leeds city centre in a "managed area" for sex workers.
He said Miss Pionko was found by another sex worker who told another member of the public.
Mr Atkinson said: "We can confirm that the victim was a sex worker and the incident has taken place in the managed area where sex workers operate within a defined area during set hours.
"We are therefore appealing to anyone involved in any aspect of sex work in the managed area in Holbeck to let us know anything they have seen or heard that could assist the investigation."
Police sealed off the Emmanuel Trading Estate where the injured Miss Pionko was found.
Officers could be seen searching, and a white forensics tent was erected in one corner of the car park.
Superintendent Sam Millar, who heads the city's community safety partnership Safer Leeds, said: "The managed area has been operating in Holbeck since last year following a partnership agreement between the police, council and other key agencies after many years of an enforcement-based approach that did little to change the situation.
"The aim has been been to reduce the impact of sex work on nearby residential communities and provide an environment where sex workers are more likely to engage with third sector agencies who can offer them support, ultimately to exit this activity.
"The area is regularly patrolled by officers and we have seen a large increase in sex workers having the confidence to report offences committed against them to the police.
"It has seen some significant successes, including the imprisonment of dangerous offenders who presented a risk to the wider community. Those prosecutions would not have been possible without the vastly improved relationship between sex workers and the authorities that the managed area has brought.
"Clearly our focus now is on tracing the person responsible for this murder and we hope that improved relationship will assist the investigation."
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."