A fourth man has faced court charged with allegedly planning a terror attack in Melbourne's CBD on Christmas Day.

Ibrahim Abbas, 22, was charged at an out-of-sessions hearing last night with one count of preparing for or planning a terrorist attack.

Mr Abbas appeared in the Melbourne Magistrates' Court today with a black eye and flanked by two guards in the dock.

His lawyer requested her client see a doctor to treat possible head injuries sustained in his arrest.

"Sometimes clients get injuries during the arrest, so I've mentioned in court that he will need to be seen by a doctor because of the head injuries and eye injuries," lawyer Therese Wattis told 9NEWS.

Mr Abbas, who requested a prayer mat and a Koran during the hearing, was remanded in custody until his next court appearance in April.

Ahmed Mohamed (L) and Hamza Abbas (R). (9NEWS)

A court artist's impression of Abdullah Chaarani, 26. (9NEWS)

Mr Abbas' court appearance comes after Abdullah Chaarani, 26, Hamza Abbas, 21 and Ahmed Mohamed, 24, were all charged with one count of preparing for or planning a terrorist attack yesterday.

The men made no application for bail in the Melbourne Magistrates' Court yesterday and were remanded in custody until their next appearance on April 28, 2017.

Jessie Smith, the lawyer acting for Hamza Abbas, told Magistrate Timothy Burke her client sustained injuries to his face, back, hip and left shoulder during the raids.

Ms Smith asked that the 21-year-old be seen by a doctor and that the court note he is vulnerable due to his age and the nature of the charge.

"He does have soft tissue injuries from the arrest," Ms Smith said, adding he had a pre-existing back injury that requires treatment.

Four women were in court to support Mr Abbas and Mr Mohamed.

One of them began to cry as Mr Mohamed was brought into the dock.

The men were arrested as part of a series of raids conducted by Victoria Police and the Australian Federal Police on Thursday night and yesterday morning.

A 21-year-old Gladstone Park man was released without charge. A 20-year-old woman and a 26-year-old man, both from Meadow Heights, were also released without charge.

Police allege the plot was to have targeted iconic Melbourne landmarks including Flinders Street Station, Federation Square and St Paul's Cathedral.

Of the five men who were taken into police custody, four are Australian born and a fifth is an Egyptian-born Australian citizen.

Prime Minister Malcolm Turnbull urged Australians not to let alleged terrorists succeed in frightening and dividing the nation.

"What these criminals seek to do is kill. But also, to frighten us and to make us abandon our Australian way of life. We will not let them succeed," he said.

Five properties in Gladstone Park, Flemington, Meadow Heights, Dallas and Campbellfield. (AAP)

"We will continue to go about our daily lives as we always have."

Chief Commissioner Graham Ashton said police had been watching the alleged plotters for some time, and believed they were preparing a multi-mode attack.

"Over that last fortnight that has accelerated," Mr Ashton said.

Police believed the threat had been neutralised through the raids, he said.

Premier Daniel Andrews said there will be extra police on the streets on Christmas Day to ensure the public feel safe.

A heavy police presence outside Melbourne Magistrates Court today. (9NEWS)

"(These alleged planned attacks) were not acts of faith - they were in their planning, acts of evil," Mr Andrews said.

Mr Ashton said police believe the plotters planned to use an explosion and other weapons in the attack.

"We believe it was certainly going to involve an explosive event," Mr Ashton said.

"These are self-radicalised... (but they were) inspired by ISIS and ISIS propaganda.

"If this had got under our guard this would have been a significant attack."

It is also alleged the makings of an improvised explosive device were found in the raids, which involved around 400 police officers.

Premier Andrews said people should go about their business safe in the knowledge that Victoria Police is protecting them.

"What (allegedly) 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.

The nation's terror threat remains at probable.