NSW's Joint Counter-Terrorism Taskforce (JCTT) says a 21-year-old man from the state's South Coast has been charged with planning a terrorist act.

Key points: Officers searched Joshua Lucas's home following escalating extremist posts online

Officers searched Joshua Lucas's home following escalating extremist posts online Police allege Mr Lucas was trying to purchase military firearms

Police allege Mr Lucas was trying to purchase military firearms Inquiries are continuing into his online and real-world associates

Joshua Lucas was arrested as part of a joint Australian Federal Police and NSW Police investigation into extreme right-wing behaviour, and did not apply for bail when he appeared in Nowra court today.

Australian Federal Police Commissioner Scott Lee alleged Mr Lucas was trying to "source material in relation to the construction of an IED".

"It will be alleged the man was attempting and planning to purchase or acquire military equipment, including firearms and items capable of making improvised explosive devices," he said.

Officers from the JCTT will also allege Mr Lucas expressed support for extreme right-wing ideology.

The investigation began in February, after NSW JCTT investigators became aware of several online posts they claim contained extreme political and anti-government ideology.

A search of Mr Lucas's home on Sanctuary Point Road in Sanctuary Point, revealed numerous electronic devices, tactical equipment and three paintball guns.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 3 seconds 1 m 3 s A joint investigation between state and federal police led to a search of Mr Lucas's Sanctuary Point home.

Officers also searched the Parma home of an associate of Mr Lucas, seizing four registered firearms.

Registered firearms were seized when police searched a Parma home. ( Supplied: AFP )

"What we know is this person had anti-government sentiment, he was anti-Semitic, he has neo-Nazi interests and he has anti-Indigenous interests," NSW Police Assistant Commissioner Mark Walton said.

He said there was no ongoing threat to the community, and encouraged people to report suspicious online behaviour.

"Be aware of the online activities of your children," he said.

"There is no place for violent extremism in our community and we need to continue to unite in condemning this behaviour."

Mr Lucas's case was adjourned until May, with an application made to have the matter heard in a Sydney court.

The offence carries a maximum penalty of life imprisonment.