Motorists were delayed as protesters blocked the opening of the Land Forces exposition at the Melbourne Convention and Exhibition Centre on Wednesday morning, shutting several roads and bridges to traffic.
The state's treasurer warned anyone who did not need to be in the area to stay away.
"If you have no business being there, if you're not there protesting, I wouldn't encourage anybody to be there," Tim Pallas said on Tuesday.
Yarra Trams has warned commuters of disruptions to several city-bound services, including the routes 96 and 109.
The citybound exit of the West Gate Freeway was closed at Montague St, causing delays for those using both the West Gate and Bolte Bridges.
Anti-war protesters say their rally was triggered by the government's stance on the Gaza conflict. (Joel Carrett/AAP PHOTOS)
Disrupt Land Forces spokeswoman Jasmine Duff said the protest was triggered by the government's stance on the conflict in the Middle East.
"We're protesting to stand up for all those who have been killed by the type of weapons on display at the convention," she said.
"Many of the weapons inside the convention centre are advertised as battle-tested. In the context of Israeli weapons firms, which are present, this means tested through killing civilians in Gaza."
Federal Greens leader Adam Bandt said he hoped the demonstrations would not descend into any violence.
"I always urge peaceful protests. I think peaceful and non-violent protest is critical in this country," Mr Bandt told ABC's Radio National.
"What people are protesting about here is an end to the escalation of war, of starting to treat weapons manufacturing now as somehow an inherent good."
Mr Pallas said police had asked the state government for additional funds to cover the event, estimated to cost $10 million to $15 million.
Police are out in force at an anti-war protest outside a weapons expo in Melbourne's CBD. (Joel Carrett/AAP PHOTOS)
Victoria Police expects it to be their biggest operation since chaos surrounding the World Economic Forum in 2000, with hundreds of regional officers travelling to Melbourne for the event, along with general duties officers and specialist police.
These include the Public Order Response Team, Highway Patrol and Mounted Branch.
A police spokesperson said major efforts were under way to ensure the "highest level of safety and security" at the event.
The Land Forces International Land Defence Exposition runs from Wednesday to Friday.
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