Two men have been charged over the alleged rapes of two young girls in Werribee in early December.

One of the victims was aged under 16 and the other under 12.

Both of the men are charged with assaulting both of the girls on December 3 in Werribee.

A 21-year-old Noble Park man was arrested and charged on Saturday night with two counts of sexual assault of a child under 16, three counts of sexual penetration of a child under 16, and sexual penetration of a child under 12.

On Tuesday, a 23-year-old Werribee man was charged with three counts of sexual assault of a child under 16, sexual penetration of a child under 16 and four counts of sexual penetration of a child under 12.

The 21-year-old will appear before the Melbourne Magistrates Court on January 14 while the 23-year-old will not appear until May 6.

Police have so far not released further details of the circumstances of the alleged assaults.

The investigation was carried out by the Westgate Sexual Offences and Child Abuse Investigation Team.