A woman remains in intensive care with a serious throat injury after she was attacked in central Christchurch.
Amelia Rayner, 29, had left the Electric Avenue festival in Hagley Park when she was attacked at the corner of Salisbury Street and Park Terrace about 11pm on Saturday.
Police suspect she was punched in the throat.
Her boyfriend, who was with her, suffered a minor injury, but did not see the attack, Detective Senior Sergeant Mark Worner said.
Investigators want public help to identify the offender. They had been unable to speak to Ms Rayner, who was in Christchurch Hospital, because of her injuries.
"She has suffered a serious injury to her throat [and] ended up in ICU in hospital," Mr Worner said.
"It's suspected of being a punch to the throat."
Mr Worner said police had received a few calls from the public about the incident, but needed more.
"We're really relying on the media to give us some leads."
He said officers would look to source CCTV footage if the public did not lead police to the offender.
Anyone with information on the assault, or who saw what happened, was asked to phone the Christchurch police on (03) 363-7400 or Crimestoppers on 0800 555 111.