The 49-year-old, whose name is listed on the NSW Child Protection Register, is wanted on an arrest warrant for child sex offences.

Police say his is from the Illawarra region and that a recent photograph suggests he is sporting a beard.

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He was last seen in the Unanderra/Figtree area in early April 2020 and has been known to frequent the Illawarra and Tweed Heads/Byron Bay area.

Mr Wilhelm is described as being of Caucasian appearance, 185cm tall, 110kg with a large build, short brown/grey hair that is balding on top, a brown/grey unkept beard and is known to wear small dark framed reading glasses.

Detectives from Wollongong Police District are seeking information from the community about Mr Wilhelm's current whereabouts.

Anyone who sees him is urged not to approach him and to contact Triple Zero (000) immediately.

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Wilhelm relocated from Western Australia to Tweed Heads in August 2016 within months of departing prison, where he served a five-year term for possessing child pornography.

He was placed on the NSW Child Protection Register when he arrived in the state, but allegedly failed to report his change of address, as required under NSW law, when he moved to Unanderra to live with his father in October the same year.

The register, designed to monitor the movements and personal information of people convicted of a serious violent or sexual offence against a child, relies on offenders self-reporting any changes to their living circumstances.

He lived in the Illawarra free from scrutiny and monitoring by local police for more than a year until October 2017, when he was accused of assaulting his father and came under police scrutiny.

He was then charged with three counts of failing to comply with reporting obligations.