A 15-year-old boy who was charged over a plot to carry out a terrorist attack at an Australian Federal Police building used the code word ‘banana’ to discuss firearms in conversation with his co-accused, a court has heard.

In a bail hearing at Parramatta Children’s Court, in Sydney, on Thursday evening, the court heard the boy had sent a message to another man that read: 'I'm going to get to paradise through banana.'

It also heard the boy made 'hundreds' of phone calls to other people previously raided by police.

The teenager, whose name cannot be published for legal reasons, has reportedly been radicalised and monitored by police for more than a year.

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A 15-year-old boy and a 20-year-old man (above) have been charged over an alleged plot to carry out a terrorist attack on a government building after five homes were raided in Sydney's south-west

He was also convicted of possessing an illegal firearm just four months before he was arrested on Thursday morning after five homes were raided in Sydney's south-west.

The prosecution argued there was an apparent risk in granting him bail, and said if not for police monitoring the boy 'we could be looking at a more serious situation'.

Senior Sergeant Wells also said it was clear the boy's family was unaware of his actions with other accused parties.

The 15-year-old's defence argued the boy was young at the time of previous raids, and said his behaviour then had not been concerning enough for him to be denied bail following the 2014 incident.

The pair have been charged with a count of conspiracy to conduct an act in preparation for a terrorist attack. It has since emerged the boy had been radicalised for more than a year

He also said the previous extreme influences on the boy have been removed, and claimed the boy was willing to not have a mobile phone if he was released.

'The risk to the community are at the very stretch of the imagination,' the defence told the court.

'If nothing happened after the December 2014 raids, the risk is less substantial now.'

The court also heard the boy has 'conducted himself according to (previous) orders of the court'.

Prosecutor Snr Sgt Wells asked the boy’s psychologist Hanan Dover if she believes the 15-year-old is easily influenced - especially by older people.

Mr Wells highlighted the co-accused were all older than the boy.

He also showed the court a number of photographs of the 15-year-old, which included images of him posing with a gun and others of a beheading and one of ISIS members stood in front of a flag while pointing to the sky.

A further three homes in Bankstown, Merrylands and Wiley Park were also searched but no-one was arrested

The pictures were taken from the 15-year-old's phone when he was arrested in December 2014.

Mr Wells asked Ms Dover if the possessions images of the beheading, which included a before and after photograph, should be considered a cause for concern and inconsistency in behaviour, due to the 15-year-old's apparent 'shock and horror' felt following raids at his home.

Ms Dover argued the 15-year-old had been mentally harmed by raids on his property in 2013 and December 2014, when he was also charged.

'He suffered...I first saw him in January... prior to those raids he would have been of normal adolescent fortitude.

'He told me he feared for his safety... He remains sleeping in his parents’ bedroom.'

She also said he has frequent nightmares as a result of the raid and has ongoing 'trauma-like' conditions.

'He didn’t feel safe at all,' she said.

The teenager and the Raby man (above) were arrested as part of Operation Appleby and they were involved in an alleged plot discovered by police in the raids in December 2014

OPERATION APPLEBY: WHAT HAS HAPPENED SO FAR A 15-year-old boy from Georges Hall and a 20-year-old from Raby both charged with conspiracy to conduct an act in preparation for a terrorist act

The teen is expected to face Parramatta Children's Court on Thursday

The 20-year-old is expected to face Campbelltown Local Court on Thursday afternoon

Homes raided in Bankstown, Wiley Park and Merrylands - no arrests made at these homes

Three men, believed to all be inmates at the Goulburn Supermax prison, have also been arrested

They are expected to be charged and to also face court on Thursday afternoon

The trio are already before the courts on related and unrelated matters.

All arrested men are associates of those connected with the murder of police accountant Curtis Cheng outside Parramatta police headquarters in October

Charges relate to material seized by Joint Counter Terrorism Team officers in December 2014

Police seized documents in December 2014 that 'talk about a plan' naming government buildings 'specifically the AFP building'

Thursday's arrests relate to a further alleged plot

The original plot involved the alleged planning of an attack on a random member of the public

Police say the second plot 'may have involved an attack on a government building, whether that be AFP or police'

Both plots relate to activities allegedly planned in 2014 and police say there was no immediate threat at the time of Thursday's arrests

The Joint Counter Terrorism Team has made 11 arrests as part of Operation Appleby, which began in 2014 Advertisement

Ms Dover also said he would be at risk of self-harm if left on his own. And said she doesn't not believe he is a risk to the public.

'He has showed remorse,' Ms Dover said.

The psychiatrist also claimed the 15-year-old made 'exaggerated comments' to try to fit in with people around him, which contributed to previous raids.

She recommended he should be released in the custody of his parents, who she described as 'very supportive'.

Defence lawyer Charles Waterstreet argued his client had a very low risk of reoffending, and that he was attempting to form more 'appropriate' friendship groups.

His bail hearing has been adjourned until Friday morning.