Dozens of loudspeakers are being installed around Melbourne's CBD as part of a new emergency warning system, which police will test this month to give the public "a feel" for the sound of the alert.

Sixty-five sets of speakers have already been installed at city sites where security cameras are in place, including Bourke Street Mall and Flinders Street Station.

The speakers operate like this: A police officer will read out a message to help direct people in the event of an emergency

A police officer will read out a message to help direct people in the event of an emergency The message may be sent out in one location, or across the city

The message may be sent out in one location, or across the city It will inform people to move to a certain location or take shelter in a nearby area or building

It will inform people to move to a certain location or take shelter in a nearby area or building The loudspeakers will be used alongside other warnings such as text messages or alerts on social media

Police Minister Lisa Neville said another 31 CCTV cameras would be installed over the next 12 months, along with the loudspeakers, to help keep people safe in a major emergency.

She said a test message would be transmitted over speakers at the State Library on December 28 to trial the system.

The message will include a warning signal and notify people it is a test only.

Traders in the area will be informed the test is happening.

Ms Neville said the test message, just days before New Year's Eve celebrations, would give people a idea of what the warning will sound like.

"It's not about causing panic," she said.

"It's about making sure people have the information they need to manage a serious incident."

The loudspeakers will be installed in more than 90 locations around Melbourne's CBD. ( ABC News: Danielle Bonica )

Last month, a 20-year-old Werribee man was charged with terrorism offences after allegedly plotting to "shoot as many people as he could" at Federation Square on New Year's Eve.

Victoria Police Acting Chief Commissioner Shane Patton said Victoria was a safe place, but vehicle-borne attacks were "still a major concern" after the Bourke Street incident.

"The loud speakers will allow us to put out warning messages in the event of an incident occurring whether it be a terrorist event or whether it be another mass casualty incident, or one that's of high risk," he said.

"It will allow us to inform the public in the city where they should be going, what they should be doing and making sure they're safe and understand what's unfolding."

Concrete planter boxes have been installed in Bourke St Mall to prevent vehicle attacks. ( ABC News: Melissa Brown )

The Victorian Government has already announced it will spend $10 million to upgrade security in Victoria.

The upgrades follow a review of Victoria's counter-terrorism laws after a deadly siege in Brighton earlier this year.

The new measures include:

Protective barriers, such as planter boxes in Bourke Street Mall, to protect against vehicle attacks

Protective barriers, such as planter boxes in Bourke Street Mall, to protect against vehicle attacks Proposed counter-terror laws to detain children as young as 14

Proposed counter-terror laws to detain children as young as 14 New laws to hold adults suspected of terrorism offences for up to four days

Acting Chief Commissioner Shane Patton says vehicle attacks remain a concern. ( AAP: Joe Castro )

Meanwhile, global counter-terrorism experts will be in Melbourne over the next three days as part of an international conference to discuss terrorism prevention.

It is the first time the conference has been held outside of the United States.

Acting Chief Commissioner Patton said representatives from the Five Eyes group of intelligence agencies — the UK, US, Canada, Australia and New Zealand — were taking part.

"We hope to learn from their experiences," he said.

"We hope to expand our knowledge and understand the current threat, the future threat and the risks we're facing and how we can deal with them."