Mother of missing woman arrives in Sydney

Homicide police have joined the search for a 28-year-old Chinese woman living in Sydney who has been missing for nearly four days.

The mother of a missing 28-year-old woman has arrived in Sydney from China as homicide police investigate her daughter's disappearance.

Qi Yu was last seen by friends at a Campsie share house in the city's southwest in on Friday evening, about the time she last spoke with her family in China, NSW police said in a statement.

Police on Tuesday said the woman was still missing.

Ms Yu's friends reported her missing on Saturday morning after finding her room empty, saying it was out of character for the Chinese national.

Police found her car, a white Toyota Corolla, parked about four kilometres away on Lindsay Street in the neighbouring suburb of Burwood on Saturday afternoon.

Ms Yu's neighbour Vincent Chen said the missing woman's mother visited the Campsie house on Sunday.

"She cried and cried," he told The Daily Telegraph.

Mr Chen described the 28-year-old as "a very honest and quiet girl, a very nice girl".

There's been no sign of Ms Yu and homicide detectives have now been assigned to the case.

Investigators are asking anyone who saw Ms Yu or her car - numberplate DLK 13P - over the weekend to contact them.