Interstate police have been called in to bolster law and order ahead of what could be Victoria's biggest protest since the chaos surrounding the World Economic Forum in 2000.
More than 100 people were arrested in that rally, in scenes unusual in Melbourne at the time.
Protests kicked off earlier than expected on Friday night, despite the Land Forces expo not starting until Wednesday.
Melbourne hotels were vandalised with red paint and traffic blocked during protests held on Saturday.
On Sunday morning, a small group of protesters from Extinction Rebellion blocked Montague Street near the Melbourne Convention and Exhibition Centre where the expo is being held.
Authorities are bracing for the biggest protest in more than two decades (Joel Carrett/AAP PHOTOS)
Victoria Police said on Sunday, they would have a significant presence during and in the lead up to what will be their biggest operation in decades.
Hundreds of police have been diverted from regional areas to provide support and numerous officers can be seen in and around the building, including at all exit and entrance points.
Police also erected a ring of steel around the event, which is also expected to attract up to 25,000 activists.
That fencing has since been covered by tarps, making it difficult to see what is happening inside.
Police, using anti-terror legislation, will also have increased powers to search any person or vehicle within the area surrounding the event.
The biennial Land Forces International Land Defence Expo, previously held in Brisbane, attracts hundreds of defence personnel from around the world to the showcase of weapons and technology.
More than 800 domestic and international companies and leading organisations will take part.
Military tanks, heavy-duty trucks and semi automatic guns will be on display during the three-day event - with at least one military tank discreetly delivered under a cloak of darkness at 3am on Saturday.
Interstate police will arrive early in the week to bolster security around the expo (Joel Carrett/AAP PHOTOS)
Students for Palestine and Disrupt Wars are planning to block the opening of the convention on Wednesday, and say they have already stopped deliveries of weapons during a "peaceful blockade" on Saturday.
Blockade co-chair Bella Beiraghi said anti-war activists would flood Melbourne ahead of the expo.
"Young people from across the country are flooding into Melbourne to blockade the Land Forces convention's opening ceremony on Wednesday, because we stand against the death and destruction brought by weapons of war," she said.
Police Minister Anthony Carbines warned those who planned to cause trouble at the South Wharf event would be dealt with by the full force of the law.
"If you come into town to cause disruption ... if you come here to be an idiot, the Victorian police will deal with you swiftly," Mr Carbines told reporters on Sunday.
Interstate police will arrive early in the week to bolster policing efforts.
Lord Mayor Nick Reece urged protesters and Melburnians moving around the city to stay calm.
He said Melbourne had a strong track record in holding major events and it would continue during the weapons expo.
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