A Sydney man accused of raping of a four-year-old girl while he was working as a tutor has been formally refused bail.

Quy Huy Hoang, also known as Peter Hoang, was charged with having sexual intercourse with a child under the age of 10, with the alleged incident taking place while he was employed as the girl's maths tutor in December 2007.

Hoang, 67, was also accused of indecent assault against three other children aged between nine and 13 between February 2010 and March 2013.

All of the victims were from Sydney's Vietnamese community.

Detectives from the sex crimes squad arrested and charged Hoang yesterday.

Hoang did not apply for bail when his case was heard in Bankstown Local Court this morning because he was already in custody on existing charges.

Bail was formally refused and the former tutor will return to court in April.