It's alleged the man sexually and indecently assaulted the girls - then aged eight and nine - on multiple occasions at homes near Canberra and in Sydney's north west between 2008 and 2009.

It's also alleged he sexually and indecently assaulted a boy - then aged between 11 and 13 - at homes on the Central Coast between 2010 and 2011.

The two girls and boy were known to the man.

Police arrested the man outside a home on the central coast just after 8am on Wednesday.

He appeared before Wyong Local Court on Thursday and was refused bail.

There are 17 charges laid against him including disseminate/produce child pornography (x2), sexual intercourse with person under the age of 10 years, indecent assault person under 16 years of age (x8), take/detain person with intent to obtain advantage (x2), aggravated sex assault - victim under the age of 16 years, break and enter etc do indictable offence (x2), and enter dwelling with intent (not steal/destroy/damage).

Detectives seized 70 items including mobile phones, cameras, computers and other electronic devices from the man's home.

Investigations are continuing.

Anyone with concerns about suspected child abuse or exploitation should call Crime Stoppers on 1800 333 000 or use the Crime Stoppers online reporting page: https://nsw.crimestoppers.com.au.