A 13-year-old boy and a man, who is 27, have been arrested on suspicion of murder after a woman was stabbed to death in the street on Saturday night.
The 25-year-old victim was attacked in Rushden, Northamptonshire, at 8.30pm, police said.
She died at the scene after police and paramedics were called to Wellingborough Road.
One line of inquiry being explored is that it was a mugging that went wrong.
A second man, 27, has been arrested on suspicion of attempted murder.
Detective Inspector Pete Long, of Northamptonshire Police, described it as "an extremely tragic incident in which a young woman has lost her life".
He said he wanted to "reassure people that we are doing all we can to bring those responsible to justice".
A large team of detectives is working on the case around the clock and a number of lines of inquiry are being pursued in the fast-paced investigation, he added.
"This incident has really shocked the Rushden community, many of whom were on the scene last night, and I would ask anyone who was there and saw what happened to please come forward with your information."
A police scene is expected to be in place throughout Sunday and motorists are urged to avoid the area.
Increased police patrols are in place with response teams and neighbourhood officers reassuring members of the community.
Anyone with information should contact Northamptonshire Police on 101 or Crimestoppers, in confidence, on 0800 555111.
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