A homeless man pleaded guilty on Friday to the murder of a Chinese student who plunged to her death from a third-floor balcony in Sydney after she was repeatedly raped.

Brendan David Dennison, 27, pleaded guilty in the Supreme Court to 19 charges over the attack.

Dennison admitted murdering the teen and causing her boyfriend grievous bodily harm after breaking into the unit on Oct. 26, 2008.

The 18-year-old woman, her 19-year-old Korean boyfriend and two other female students were held at knifepoint during a frightening ordeal in their inner Sydney unit in October last year.

Police said at the time the young couple tried to escape by jumping naked from the third-floor unit onto concrete. She died, while he was seriously injured with spinal injuries.

Dennison pleaded guilty to several counts of sexual intercourse without consent against the couple, aggravated by threatening to inflict actual bodily harm with a knife, and to detaining the four students with intent to obtain sexual gratification.

He was remanded in custody and is due to be sentenced on March 9 next year.