Terror raids across Melbourne have seen seven people arrested and five placed in custody, over a suspected “explosive event” planned for Christmas Day in Melbourne’s CBD.

Close to 400 police officers commenced the raids of five properties on Thursday night, which continued early Friday morning across five of the city’s northern suburbs including Flemington, Meadow Heights, Dallas, Campbellfield and Gladstone Park.

“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.

According to Ashton, officers successfully recovered “the makings of an improvised explosive device” and the plan is believed to have possibly included other weapons such as knives and firearms.

“As a result of the investigation, we believe we have neutralised that threat,” he 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.”

ASIO and AFP officers, along with Victoria Police had been monitoring a number of suspects across Melbourne for some time.

The five men who are currently in custody and aged in their 20s are being questioned by police.

Speaking at the police press conference on Friday morning, Victorian premier Daniel Andrews called the plot “an act of 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,” Mr Andrews said.

Given the time of year with citizens planning to attend a number of events surrounding Christmas and the New Year, including the Boxing Day cricket match, the premier reassured that Victoria is a safe state.

“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,” Mr 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.”

He also took the opportunity to remind the community of the strength of its cultural diversity during this time.

“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 said.