Police in Australia are hunting for the killer of a 21-year-old exchange student who was attacked in Melbourne while speaking to her sister on a FaceTime phone call.

Aiia Maasarwe, an Israeli student who was visiting Melbourne as part of her studies at Shanghai University, had attended a comedy show and was walking from a tram stop to her accommodation in the suburb of Bundoora at about 12.10am on Wednesday morning when she was stalked and assaulted.

Police said Ms Maasarwe was talking to her sister, who was overseas, when she was attacked, about 160 feet from the tram stop. Ms Maasarwe’s sister tried to call back but was unable to make contact.

"She heard the sound of the phone falling to the ground and heard some voices and that was it," said Detective Inspector Andrew Stamper.

“This was an absolutely horrendous, horrific attack inflicted on a completely innocent young woman who was a visitor to our city."