Victorian police have released photos of clothing believed to belong to the alleged killer of a 21-year-old international student.
Victoria's homicide squad has confirmed international student Aiia Maasarwe was on the phone to her sister when she was attacked in Melbourne shortly after midnight on Wednesday.
"We're pretty certain she was involved in a conversation with her sister who was overseas at the time of the attack," Detective Inspector Andrew Stamper said.
"She heard the sound of the fall, the phone falling to the ground and heard some voices and that was it."
The body of the 21-year-old Palestinian Arab, who was an Israeli citizen, was found just metres from a tram stop at Bundoora on Wednesday morning.
Police believe she had recently alighted the 86 tram on her way home after attending a comedy show in North Melbourne. A passerby located her body on Main Drive, near Plenty Road, at about 7am.
Inspector Stamper said police are treating the incident as a random attack.
"We've got an unknown offender, we don't know ... there was nothing in her background that this was anyone known to her," he said.
The homicide squad have released images of a T-shirt and cap that were found at the scene, believed to belong to the attacker.
"We're again desperate for anyone in the community that may know anyone who was wearing or owns these items of clothing to contact Crime Stoppers as a matter of urgency," Inspector Stamper said.
"Someone has come home on Tuesday night, or the early hours of Wednesday morning, maybe with blood on them, missing items of clothing, somebody knows about this and we need help."
Police believe the items - a black baseball cap with the numbers 1986 on the front and a grey and black t-shirt - are Cotton On brand and a number of years old. Inspector Stamper said it's possible they were left behind to get rid of evidence.
He refused to comment on the nature of the assault but said it was a "horrendous, horrific attack".
"We've had people working through the night on this, both from within the crime department and from within north-west metro division five. Every available resource is being poured into this investigation."
Detectives also released CCTV image which shows the clothing she was wearing that night, in the hope someone saw her on the night and can help police track her exact movements.
Ms Maasarwe had previously studied Chinese and English at Shanghai University before moving to Victoria to study at La Trobe University.
Members of her family arrived in Australia this morning.
Anyone with further information should contact Crime Stoppers on 1800 333 000