Suicide attacks, bombings, and random stabbings – that was how four Melbourne men allegedly planned to inflict mass casualties in a series of coordinated terror strikes on Christmas Day, investigators believe.

New details from the weeks-long investigation into the terror plot are emerging as three men - Abdullah Chaarani, 26, Hamza Abbas, 21, and Ahmed Mohamed, 24 - faced charges in Melbourne Magistrates Court on Friday afternoon.

A fourth terror suspect, identified only as a 22-year-old man from Broadmeadows, was charged later on Friday evening and is due to appear in court on Saturday, ABC reported.

Three others, including a 20-year-old woman, were also arrested but later released without charges. Among them was a young IT worker, Zakaria Dabboussi, who was briefly detained and but released without being charged, according to police and media reports.

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Abdullah Chaarani, 26, appearing in the Melbourne Magistrates Court on Friday. Artist's sketch

Hamza Abbas, 21, left, and Ahmed Mohamed, 24 are depicted in this court sketch

Family members of one of five men charged over an alleged terror plot leave the Magistrates Court in Melbourne on Friday

A family member of one of the five terror suspects is pictured leaving court in Melbourne on Friday

Mr Mohamed gestured at some veiled women, who were later observed allegedly attacking a photographer outside court, according to the Herald Sun

Ahmed Mohamed, 24, is seen leaving Melbourne Magistrates Court on Friday after he was charged with preparing and planning a terror attack

The four suspects were rounded up by heavily armed officers in a series of raids across Melbourne's north and west on Thursday night and Friday morning, the Age reported.

Police were hoping to wait another 48 hours before making the arrests, but decided to move in quickly after observing some of the suspects allegedly conducting surveillance operations near Melbourne landmarks Federation Square, St Paul's Cathedral and Flinders Street Station, police sources told the Age.

Police believe the suspects were planning to attack general duties police as the officers responded to emergency calls, according to the Age.

During the raids, investigators seized what Victoria's Chief Commissioner Graham Ashton called ‘the makings of an improvised explosive device,’ as well as computers, the Age reported.

Ashton said the suspects were believed to be 'self radicalised... but inspired by ISIS and ISIS propaganda.'

The three suspects who appeared in court were charged with 'preparing for, or planning, a terrorist act.' None of the three applied for bail as the court heard it would take weeks for police to process evidence collected in the raids.

Mr Charaani, upon being charged, 'stretched his neck and nodded to two completely veiled women sitting in the public gallery,' the Herald Sun reported.

Mr Mohamed gestured at the same women, who were later observed allegedly attacking a photographer outside court, according to the Herald Sun.

An attorney representing Mr Abbas said he required a nurses attention for face, hip, back and shoulder injuries sustained during his arrest, according to the Herald Sun.

This map shows where police raided several homes on Thursday night and Friday morning in order to thwart what investigators believe would have been a series of terror attacks in Melbourne

Police said they managed to foil a terror plot to attack multiple locations in Melbourne's CBD on Christmas Day after raids (pictured) across the city

Police allege they uncovered the 'makings of an explosive device' during the raids

It will reportedly take weeks for police to collate all the information gathered in the raids

Police investigate the scene where a house was raided in Meadow Heights

Police remained at a property in Meadow Heights on Friday following raids on Thursday night

This picture shows alleged terror suspect Hamza Abbas, according to the Age. Abbas, 21, was charged with preparing for a terror attack

Alleged terror suspect Hamza Abbas is seen posing on a tank in this social media picture

The family of Mr Dabboussi, the man who was detained but released without charges, claimed 'cowardly police' were heavy handed during the raid which struck fear into the hearts of his three young cousins who became inadvertently caught up in the search.

Mr Dabboussi's father, Youssef, said his son was at the gym when armed officers beat down the door and pointed their weapons at two eight-year-old children inside, the Age reported.

He has also claimed his son Mohamed was assaulted by officers carrying out the search warrant, which resulted in a laptop being seized.

Mr Dabboussi's 12-year-old nephew Mahmoud Taleb said he jumped up off his bed and laid on the floor face down when he heard the officers enter the house.

Police have foiled an alleged terror plot to attack iconic Melbourne locations including Melbourne's Flinders Street Station (pictured) on Christmas Day

Federation Square (right) and St Paul's Cathedral (left) were also to be targeted

But despite cooperating with their demands, Mr Taleb told The Age he was knocked over the head with a gun as officers kicked and demanded he tell them where the 'bombs' were.

Mahmoud Taleb was pictured on the Age website standing over a pool of blood that stained the carpet.

Mr Dabboussi later arrived at the home and was pushed face first against the driveway before he was taken into custody, the Age reported.

His father said Mr Dabboussi had been outspoken about his position on the Syrian conflict but is not an extremist, while his sister said he is 'all talk' and was planning to spend Christmas Day with loved ones in Geelong.

The Australian Federal Police, Victorian Police and ASIO were involved in the raids which started at around 8pm on Thursday and continued into Friday.

Police in heavy body armour gathered in Broadmeadows on Thursday night before being deployed to suburbs across the city overnight.

A forensic investigation was still underway on Friday afternoon at the property in Meadow Heights where police are believed to have found 'the makings of an improvised explosive device'.

A woman wearing a niqab chats with a police officer outside a home in Melbourne

A woman approaches a group of police officers as they continue conducting a search warrant

A man holds a young girl's hand as he approaches the police raids in Meadow Heights

Four people are in police custody and were charged for their alleged involvement in preparing to commit a terrorist attack

Officers were still conducting a search of a home in Meadow Heights (pictured) on Friday

Police Chief Graham Ashton and Premier Daniel Andrews said there had been seven arrests. Four of those detained were charged, and three were let go without charges

A forensic investigation is still underway at a property in Meadow Heights where police are believed to have found 'the makings of an improvised explosive device'

TERROR RAID ARRESTS Counter terrorism officers arrested six men and one woman during raids across Melbourne on Thursday night and Friday morning. A 20-year-old woman and a 26-year-old man, both from Meadow Heights, were released without charge. A second man was also released without charge. Four Australian men remain in custody. Police said charges relating to preparing a terror attack were laid on: A 24-year-old man from Meadow Heights

A 26-year-old man from Dallas

A 21-year-old man from Flemington Advertisement

Mr Ashton said there will be heightened security at holiday events over the next week, including the Boxing Day Test match and Christmas Carols concert, but assured the public there was no intelligence to suggest there were any other threats planned.

Premier Daniel Andrews said condemned the terror attack, but urged Victorians not to consider it an 'act of faith'.

'What was being planned was not an act of faith, was not an act of religious observance, it was instead in its planning, an act of evil, a criminal act,' he said.

'All of us, particularly at this special time of the year, should remember and understand that our values, our multiculturalism, our diversity, is a great strength.'

'Perhaps our greatest strength, even when confronted by these sorts of challenges,' he added.

Premier Daniel Andrews (pictured) condemned the alleged planned terror attack, but urged Victorians not to consider it an 'act of faith'

Four were detained after police raided numerous properties across Melbourne's north west on Thursday night and Friday morning (pictured)