A murder investigation is under way after a woman, who was found with serious head injuries, died in hospital.
Police were called after the 36-year-old was discovered by paramedics in Ilford, east London, in the early hours of Sunday morning.
She was taken to hospital but died from her injuries.
The victim, who has not yet been named, had been walking along the Cranbrook Road in the direction of Gants Hill Station when she was subjected to the "horrific assault", the Metropolitan Police said.
Scotland Yard has been carrying out "urgent inquiries" to identify the woman and has said her family has been informed.
Forensic officers are at the scene, which has been cordoned off. No arrests have yet been made.
'I urge you to be alert but not alarmed'
Software developer Amir Ahmed, who lives along the street, said he realised "something was amiss" when he got up to take his two sons to football practice and the road was blocked off by police.
"It rang alarm bells and I knew it was something serious," the 43-year-old told Sky News. "I would say at least two dozen officers were there."
"It's just shocking that people can't even walk safely anymore... it shows danger can happen anywhere," he added.
Mr Ahmed explained that the road is constantly in use, with cars often driving down it even in the early hours of the morning.
"It seems like a stranger must have attacked somebody and the police have told people to be alert, which has raised suspicions," he said.
Officers have told local residents to expect a "significant police presence" in the area over the coming days.
"I understand that for women, particularly locally, this is an incredibly distressing incident and I urge you to be alert but not alarmed," said Chief Superintendent Stuart Bell.
Officers have asked anyone who witnessed the incident or was in the area between 2am and 3am to get in touch.
"It is vital that my officers speak with every possible witness and everyone with information that may assist the investigation," said Detective Chief Inspector Mark Rogers.
"We also want to hear from anyone who saw anything suspicious in the wider Ilford area overnight."
Anyone with information or footage, or any witnesses, is asked to call the major incident room on 0208 345 3715.