NSW man charged over child sex abuse

A 68-year-old man has been charged over the abuse of four young children of a family friend in Sydney's west.

Three girls and one boy were allegedly sexually assaulted by the man between 2004 and 2008, police said.

Child Abuse Squad detectives were tipped off about the alleged abuses in August, which led to the arrest of the Auburn man on Wednesday.

A majority of the alleged offences were committed while the children were under the age of 10, at properties in Auburn and Merrylands in Sydney's west.

The man was charged with 39 offences relating to sexual and indecent assault of the children.

He was refused bail to appear in Burwood Local Court on Thursday.