Knife found at scene of alleged murder

Police believe they have found the knife that was used in the stabbing death of a man in western Sydney.

(AAP)

A killer has left behind a knife after stabbing a man to death in a western Sydney apartment block, police say.

The victim, believed to be in his 20s, was found facedown with stabs wounds in the Auburn flat in the early hours of Tuesday.

Police Superintendent Phillip Rogerson said a knife, believed to be the murder weapon, was found at the scene.

Detectives are interviewing several people who were at the apartment at the time.

However, officers believe the killer is on the run.

Supt Rogerson said they were still trying to identify the man.

Neighbours were woken just before 1am (AEDT) to the sounds of fighting and shouting at the Marion Street block.

Police would not comment on reports they were searching for the man's flatmate.