Dee Willis, 28, received a wound to her upper body during the attack at around 11pm on Tuesday in Bellenden Road, close to Peckham High Street in south east London.

Ms Willis was taken to Kings College Hospital but was pronounced dead shortly after midnight. Neighbours said that Ms Willis recently miscarried twins.

Detectives said they were looking for a female suspect, believed to have acted alone.

Meanwhile, the sister of 16-year-old Ben Kinsella, who was stabbed to death at the weekend, has appealed for crucial witnesses to come forward and "make a stand to help the police".

Former EastEnders actress Brooke Kinsella thanked members of the public for providing "significant information" but added: "Unfortunately, the police have told us that they know of others who can provide crucial evidence but they have chosen not to tell the police what they know."

Speaking at a press conference in Islington, north London, she described her brother as "entirely innocent" and said: "All we've got left of Ben now is memories and that's not very fair, in my eyes."

The GCSE student died in the early hours of Sunday morning after a fight in a bar spilled out on to the streets.

Ben was stabbed a number of times during the incident on York Way, Islington, before dying in the arms of his friend Louis Robson, 16, the son of Birds Of A Feather actress Linda Robson.

Three young men, two aged 18 and one aged 19, are in custody after being arrested by detectives investigating the murder.