A man accused of plotting a mass casualty terror attack targeting public buildings and places of worship has been hit with a slew of fresh charges, including possession of child abuse material.

Jayson Joseph Michaels detailed his alleged plan for a violent assault on Western Australia’s police headquarters, the state’s Parliament House and mosques in a diary, believing it would be worse than the Bondi Beach mass shootings.

The 20-year-old had initially faced five charges, including acting in preparation for a terrorist act, after police seized the diary in a raid on his parents’ home in the town of Bindoon, north of Perth, in February.

But on Wednesday, Stirling Magistrates Court in Perth heard Michaels had been charged with the six new offences.

They are possessing a bulletproof vest, two counts of possessing violent extremist material on electronic devices, two counts of possessing objectionable material related to computer games, and possessing child abuse material.

Michaels, who appeared via video-link from Casuarina Prison, confirmed he understood the charges and wasn’t required to enter a plea.

He was remanded in custody to reappear in the same court on July 8.

Michaels had originally faced three firearms and ammunition charges and one of allegedly using a carriage service to menace, harass or cause offence.

His diary allegedly contained entries that amounted to a list of actions he planned to carry out, including making weapons and body armour for a “day of justice”, prosecutors have previously told the court.

Michaels allegedly planned to buy a 3D printer to make a gun and got a job where he could access bomb-making materials, but left empty-handed after one day.

He also compared the Bondi Beach attack to his own terror plot and wrote notes about how it might impact it, Commonwealth prosecutor Kirsten Nelson told a failed bail application hearing in April.

“What I want to do to both these groups pales in comparison to today,” he allegedly wrote after the December 14 shootings that killed 15 and injured many more.

“What will they all think when my face is on TV?”

Michaels allegedly accessed online material about extremist white supremacist ideology, some of which was described as a manifesto and instruction manual from a declared terrorist organisation.

He wrote about researching entry points and door locks at his target locations and considered using a van that looked like an ambulance to get away.

He also allegedly penned a note about buying a ballistic helmet, designing and building body armour or an Iron Man-style metal suit.

“I think I’m addicted to the (Watch People Die) website,” he wrote in another diary entry.

The website was open on his computer when police burst into his bedroom, allegedly finding two guns, 900 rounds of ammunition and various knives.

The court has previously heard Michaels was an isolated and depressed young man who had no intention to carry out the plan.

-AAP