23/12/2016 9:10 AM AEDT | Updated 24/12/2016 8:12 AM AEDT

Fourth Man Charged In Melbourne Over Christmas Terror Plot

Police say they foiled a major terror attack, planned for Federation Square.

A fourth Melbourne man has been charged with terrorism offences and will face court later on Saturday accused of planning a terror attack, possibly on Christmas Day.

On Friday, three men were denied bail when they faced court charged with planning a major terrorist attack in central Melbourne, potentially on Christmas Day.

Police allege the men were self-radicalised and were inspired by the so-called Islamic State group. Extra security will be provided at public events in Melbourne in the coming days.

Police swept on a number of locations on Thursday night, arresting seven people in multiple terror raids across Melbourne, with police claiming to have foiled a major "multi-mode" attack planned for the CBD.

Around 400 officers from the Victorian and Australian Federal Police executed the raids on Thursday night, targeting five addresses in suburbs in Melbourne's north; Flemington, Meadow Heights, Dallas, Campbellfield and Gladstone Park. Five men remain in custody, aged in their 20s, and are expected to be charged. Police said the men were Australian-born except one Egyptian-born man.

"In relation to that threat, we believe that there was an intention to conduct what we call a multi-mode attack, possibly on Christmas Day, the possible locations that we have been working on have been Federation Square, Flinders Street Station, and St Paul's Cathedral," Victoria Police Chief Commissioner Graham Ashton said.

Ashton said the plan possible included explosives, knives or firearms, and that officers had recovered "the makings of an improvised explosive device." Prime Minister Malcolm Turnbull called it "one of the most substantial terrorist plots that have been disrupted over the last several years."

"As a result of the investigation, we believe we have neutralised that threat," Ashton said.

"We are anticipating that as a result of that questioning we will present a number of persons before the courts in the early afternoon, seeking to charge them with acts in preparation of a terrorist event."

Speaking in Sydney, Federal Police commissioner Andrew Colvin said the alleged plot "certainly concerns me more than any other event that I've seen."

Turnbull urged citizens to report suspicious activity to authorities.

"We should call the national security hotline, 1800 123 400. Speak up. Don't ever be afraid of making a call of letting the police know," he said.

"Our police and intelligence services keep us safe because citizens keep them informed. It is up to all of us to keep our eyes open."

At the police press conference, state premier Daniel Andrews called the planned attacks "evil".

"What the police will allege, was not an act of faith, not an act of religious observance, it was, instead, in its planning, an act of evil, a criminal act," he said.

With Christmas coming up, plus the Boxing Day cricket match and New Year's celebrations, the premier sought to assure citizens of safety measures.

"All Victorians should know and understand there will be an increased police presence at large gatherings, right across the city and state, over this weekend," Andrews said.

"There already would have been significant additional Victoria Police resources deployed because of the nature of some of those gatherings, but... there will be additional members of Victoria Police providing additional support to the community."

Andrews also called for calm and strength in the community.

"My message to all Victorians is we should cherish the diversity that makes us a stronger community. We should cherish the diversity that makes us the envy of so many other parts of the world," he added.

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