A 22-year-old man has been charged with extensive child sexual assault offences.
A WA Police spokeswoman said Child Abuse Squad Detectives had charged an Armadale man on June 25.
"It is alleged that within the last 18 months, the man sexually assaulted a four-year-old girl and committed further sexual offences against her nine-year-old sister," the spokeswoman said.
The police spokeswoman said the charges followed forensic analysis of seized computers and electronic devices:-
• 34 counts of Sexual Penetration of a Child Under 13 years;
• 38 counts of Indecent Dealing of a Child Under 13 years;
• 34 counts of Indecently Record a Child Under 13 years;
• 3 counts of Encourage/ Incite a Child Under 13 to engage in Sexual Behaviour;
• 1 count of Persistent Sexual Conduct with a Child Under 16 years; and
• 1 count of Show Offensive Material to a Child Under 16 years.
The man has been remanded in custody and is next due to appear in the Armadale Magistrates Court on July 1.