More massive protests expected today over Melbourne weapons expo

Anti-war protestors are expected to assemble in central Melbourne for the third day in a row as organisers call for an end to a weapons conference in the city.

Specialist officers and additional police have been brought in from New South Wales as the Victorian capital braces for what's expected to be one of the biggest protests in its history.

A massive steel fence has already been erected around the Melbourne Exhibition and Convention Centre.

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Anti-war protesters already blockaded a major arterial road in Melbourne on Saturday to call on the government to shut down the military weapons convention, which doesn't kick off until Wednesday.

Police have been patrolling around the clock and 1800 officers have been diverted from duties to monitor the area. Tanks were escorted inside the expo under darkness.

Protesters say they want the Australian government to stop funding the war machine.

"There's no place for weapons in our town and people are calling for peace around the world," protester Brad Homewood said.

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Arrests have already been made over the past 24 hours and residents are warned there could be more disruptions to come.

The Montague Street off-ramp towards South Wharf was at a crawl by 2pm on Saturday as protesters descended.

One activist was locked onto a vehicle, with specialist police called in to set her free.

After about two hours of disruption, she and another woman in her 20s were arrested.

But their passion was met by fury from motorists.

"I reckon the protesters should get a job. I just finished work, I'm sure they can find work," one motorist said.

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"They're just interrupting my job, I'm just going to do the delivery," another added.

The activists want the Land Forces military weapons expo shut down.

"Land Force is a one-stop genocide shop," Homewood said.

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"We're here to say 'not in our town. Not now, not ever'."

Demonstrations are expected to ramp up over the coming days as organisers hope to see 25,000 people protesting at the Convention Centre on Wednesday.

Police fear it could be the biggest protest Melbourne has seen in 24 years.

But the force is vowing to shut them down.

Police will also be able to use special powers around the centre to move on civilians, conduct weapons searches and demand protesters to take off their masks.